What Does Viscosity Mean and Its Importance?

How does viscosity affect your engine, mileage and performance?

Motor oil viscosity is the measure of its resistance to flow. Low-viscosity oil (e.g. 0W-20) flows faster than high-viscosity oil (e.g. 20W-50).

To illustrate, think of water and honey. When poured from a container, water flows much faster than honey.

For more good information on oil viscosity including easy to understand charts, read this blog:

What Does Viscosity Mean (and How Does it Affect Your Engine)?

AMSOIL Signature Series Max-Duty Synthetic 15W-40 Diesel Oil

AMSOIL Signature Series Max-Duty Synthetic Diesel Oil

• 6X more wear protection¹
• Excellent viscosity control
• Outstanding extreme-temperature performance
• Minimizes oil consumption

Shop for AMSOIL Synthetic Diesel Oil

¹Based on independent testing in the Detroit Diesel DD13 Scuffing Test for specification DFS 93K222 using a 5W-30 as worst-case representation.

Changing The Oil In Your Motorcycle

How to change the oil in your motorcycle.

Changing the oil in your motorcycle is easy.

Step by step easy to follow information on how to properly change the oil in your motorcycle at this AMSOIL Blog.

AMSOIL vs Harley Davidson Screaming Eagle Oil

AMSOIL Synthetic Motorcycle Oil Compared to Harley Davidson Screaming Eagle SYN3

AMSOIL Synthetic Motorcycle Oil out performs Harley's Screaming Eagle Synthetic Motorcycle oil on viscosity retention. See more detailed information on this testing done by an independent lab under controlled conditions. AMSOIL Synthetic Motorcycle oil compared to Harley Davidson Screaming Eagle Motorcycle oil.

AMSOIL Upper Cylinder Lubricant

Upper Cylinder Lubricant

Preserves Horsepower and Performance

Upper Cylinder Lubricant, 6 oz. bottle

Product Highlights

Your engine’s top-end is sparsely lubricated and prone to the development of performance-robbing deposits. It’s also highly susceptible to corrosion, an issue compounded by the prevalence of ethanol in today’s fuel. AMSOIL Upper Cylinder Lubricant is designed to solve those issues. Its AMSOIL-exclusive, powerful formulation helps maximize engine power and performance while increasing engine life. And unlike competing fuel additives, AMSOIL Upper Cylinder Lubricant works.

Lubricates Top-End Components

The intense heat of combustion and limitations of the oil-control piston ring result in a lack of oil at the top of each cylinder. AMSOIL Upper Cylinder Lubricant's unique additives provide that missing lubrication to fight piston-ring and cylinder wear, maximizing engine compression and horsepower. Its lubricity improvers also aid in protecting fuel injectors and other fuel-system components from wear, helping ensure excellent performance and long-life. AMSOIL Upper Cylinder Lubricant delivers 18 percent more lubricity than Lucas* and 20 percent more than Sea Foam* for better retention of horsepower and fuel economy (see chart below).*

Lubricity Performance ASTM D6079

Inhibits Corrosion

Upper Cylinder Lubricant uses potent corrosion inhibitors to coat metal surfaces, block out moisture and stop deterioration before it starts. This is particularly important when using gasoline that contains ethanol due to its propensity to attract water and hasten corrosion. Inhibiting corrosion maximizes component life and reduces wear in the engine's top-end to guard against compression loss and maintain optimum power.

• Lubricates fuel system and upper cylinders
• Fights ethanol-related corrosion
• Helps keep injectors clean
• Compatible with capless fuel systems

Keeps Injectors Clean

Upper Cylinder Lubricant contains detergent additives designed to maintain injector cleanliness. While AMSOIL P.i. Performance Improver is designed to attack and remove stubborn injector deposits that can reduce power and fuel economy, Upper Cylinder Lubricant helps preserve injector and combustion-chamber cleanliness. Using it with every tank of fuel helps retain fuel-economy and performance gains and maximizes component life.

Capless-Compatible Packaging

Many new vehicles have replaced traditional fuel caps with capless systems. The threads on most bottles restrict them from opening the flap inside the fuel neck and make removing the bottle difficult. The AMSOIL Upper Cylinder Lubricant bottle is fully compatible with capless fuel systems. It’s easy to insert, pour and remove the bottle.

RECOMMENDATIONS

• For use with cars and trucks.
• For best results, use with every tank of fuel. Do not refill tank until almost empty.
• Treats up to 25 gallons. Add entire bottle to tank at fill-up.
• Treat large gas tanks with two bottles of Upper Cylinder Lubricant. Using more than two bottles is not recommended.
• Safe for use with catalytic converters, oxygenated gas and up to 15 percent ethanol-blended fuels. Do not use with E85 fuel.
• Do not use with two-stroke or diesel engines.

AMSOIL PRODUCT WARRANTY

AMSOIL products are backed by a Limited Liability Warranty. For complete information visit https://www.amsoil.com/about/guarantee/.

HEALTH & SAFETY

This product is not expected to cause health concerns when used for the intended application and according to the recommendations in the Safety Data Sheet (SDS). An SDS is available at www.amsoil.com or upon request at (715) 392-7101. Keep Out of Reach of Children.

* Based on independent testing of AMSOIL Upper Cylinder Lubricant, Lucas Upper Cylinder Lubricant and Sea Foam Motor Treatment obtained on 02/13/2019 using the ASTM D6079 modified for use with gasoline. *All trademarked names and images are the property of their respective owners and may be registered marks in some countries. No affiliation or endorsement claim, express or implied, is made by their use. All products advertised here are developed by AMSOIL for use in the applications shown.

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Test run of my street legal 77 AMC Gremlin at the drag strip in Lufkin, ...

How To Properly Flush a Dirty Engine

Is flushing an engine a good or bad idea?

An engine that is properly maintained should have no sludge. However, that being said, there are reasons you might encounter an engine that is sludgy. Mechanical issues such as coolant in the oil can cause sludge. Also you may have purchased an older car that you found interesting, but the engine is sludgy.

There are things to consider when flushing an engine and selection of a good quality engine flush can go a long way to having a good end result.

This blog post is the most complete and concise information you can find on flushing an engine. I highly recommend it:

"Is an engine flush good or bad?"

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The Best Synthetic Motor Oil

What is the best synthetic motoroil?

AMSOIL provided proof of superior performance for it's Signature Series Synthetic Motor Oil.

Click photo for more information.

AMSOIL Signature Series has the proof of superiority.

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Tips To Make Your Car Last Longer

Maintenance Tips to Make Your Car Last Longer

Washing your car can go a long way to keeping it from rust and corrosion.

For good information on keeping your car in new and reliable condition, read this article:

How to make your car last longer

Automatic Transmissions and How They Work

How Does an Automatic Transmission Work?

Great easy to understand article and informative video:
How does an automatic transmission work?
CLICK HERE

Motor Oil for Cold Weather

What Motor Oil is Best for Winter? (And Other Cold-Weather Questions)

Did you know that most wear occurs on cold engine start up before thick or frozen motor oil has had a chance to circulate? Synthetic motor oils are much more fluid in cold for immediate lubrication even when starting an engine in extreme cold.

Check out this great information on motor oils and cold weather.
Synthetic Motor Oil and Cold Weather

Motor Oil Color and Service Life

What Your Motor Oil Color Means

John BakerJohn Baker | Jan 09, 2020 8:54 AM



An object’s color can reveal a lot about its condition. A brown apple? Probably not great to eat. A slice of green bread? Same. What about motor oil color? Can your eyes provide insight into your oil’s suitability to protect your engine?

Does motor oil that’s turned black require changing?

Not necessarily. In this case, the oil’s color is a sign it’s doing its job.

Oil naturally darkens during use for a couple reasons, including heat cycles. During your drive to work, your engine reaches normal operating temperature (typically 195ºF–220ºF [90ºC–104ºC]), heating the motor oil.

Shop AMSOIL Synthetic Motor Oil

Then the oil cools while your car sits in the parking lot. The process repeats as you run errands over lunch and when you return home.

This continual daily exposure to increased heat naturally darkens the oil.

In addition, normal oxidation can darken oil.

Oxidation occurs when oxygen molecules interact with oil molecules and cause chemical breakdown, just like how oxygen causes a cut apple to brown or iron to rust.

Soot also causes oil to turn black.

While we associate soot with diesels, today’s direct-injected gasoline engines can produce more soot than older diesels without exhaust-treatment devices. While individual soot particles are too small to cause engine wear, particles can agglomerate into larger wear-causing contaminants that can lead to wear before they lodge in the oil filter.

Just because the oil has darkened doesn’t necessarily mean it’s reached the end of its service life.

Motor oil contains detergent and dispersant additives designed to clean contaminants like soot and prevent them from depositing onto metal surfaces.

Oil that has turned black is an indication the additives are doing their job. You can read more about that here.

What about motor oil that looks like chocolate milk?

In this case, motor oil color does reflect performance…and oil that looks like chocolate milk is bad. Very bad.

Water or engine coolant have contaminated the oil, typically due to a head gasket leak.

We all know that water and oil don’t mix. When they combine in your engine, water droplets suspend in the oil and alter its appearance until it looks frothy or like chocolate milk.

The presence of water leads to foam bubbles, which rupture when pulled between engine parts during operation, leaving metal components unprotected against wear.

It also forms sludge, which can clog oil passages and ruin the engine. In this case, see a mechanic as soon as possible.

What if my oil looks or feels thin?

While not related to motor oil color, this is another frequent question we field from motorists.

Don’t take this the wrong way, but in this case go out to the garage and smell your dipstick.

Oil that has lost viscosity is often due to fuel dilution. You can usually smell gasoline or diesel fuel on the dipstick in such cases.

Fuel dilution occurs when gas or diesel wash past the piston rings and contaminate the oil in the sump. It reduces oil viscosity, which reduces the oil’s ability to prevent wear. It also leads to formation of harmful varnish and sludge.

Fuel dilution can occur if you idle your engine excessively or due to a mechanical defect. It’s also common in some modern direct-injected engines.

It’s important to note that no one can precisely measure an oil’s viscosity simply by looking at it or rubbing a little between their fingers.

As Oil ANALYZERS INC. manager Allen Bender likes to ask, “When’s the last time you had your eyes calibrated?”

Oil analysis in the only definitive way to determine the oil’s viscosity and whether it’s lost viscosity due to fuel dilution.

Shop AMSOIL Synthetic Motor Oil

My oil feels gritty? Should I change it?

When checking oil level, some motorists like to rub oil between their fingers to check for particles.

Grit or other contaminants can mean the oil has chemically broken down, but this is unlikely, especially with a top-shelf synthetic oil.

More likely, the oil filter has filled with contaminants and unfiltered oil is bypassing the filter and circulating through the engine.

The filter is designed with a bypass valve to ensure the engine receives oil even if the filter is full.

While dirty oil is preferable to no oil, it’s not a long-term plan for success. In this case, change the oil and filter.

Trust oil analysis, not your eyes

While it’s possible to get a rough idea what’s going on inside your engine due to oil color, appearance or scent, you need to perform oil analysis to find out what’s really going on.

By chemically analyzing a used-oil sample, a qualified lab can tell you if the oil contains excessive wear particles, water contamination, fuel dilution and more. Ultimately, the report will tell you if the oil is suitable for continued use or not.

It’s a cost-effective way to get the most out of your oil change…and your engine. Check out this post to see how to perform oil analysis.

Shop AMSOIL Synthetic Motor Oil

Motor oil viscosity explained

How to read an oil bottle

The Need To Do Regular Oil Changes

Why Do I Need To Change My Oil?

Dan McClellandDan McClelland | Jan 07, 2020 8:36 AM




Regardless of its quality, every motor oil eventually loses its potency and must be changed to ensure peak engine protection. Let’s take a look at what happens to motor oil over time and why you periodically need to change oil.

Losing the base

Base oils are the backbone of the finished lubricant that ends up in your engine. Over time, they lose effectiveness due to the following factors:

Oxidation

The interaction between oxygen molecules and motor oil molecules naturally leads to chemical breakdown.

Just as oxygen causes a cut apple to brown or exposed metal to rust, it breaks down base oils and reduces motor oil’s effectiveness.

Oxidation can lead to increased oil viscosity, which negatively affects energy efficiency. It also causes the formation of harmful deposits and sludge.

High heat

Today’s engines run hotter than ever before, with temperatures up to 235°F (113ºC), and even higher if towing or hauling.

The rate of oxidation for oil doubles for every 18°F (10°C) increase in temperature.

Moisture

Your vehicle is subjected to temperature swings, even when it is parked in the garage.

Those temperature swings cause condensation to form inside your engine, leading to water contamination.

Leaving a vehicle parked for extended periods or taking short trips that don’t allow the engine to fully warm up allow water to remain in the oil rather than evaporating and exiting through the tailpipe. Water can lead to formation of sludge…yet another reason why you must change oil.

Viscosity is a motor oil’s most important property. The lower the viscosity, the faster the oils flows, like water. Thicker oils flow more slowly, like honey.

Viscosity loss

A lubricant’s viscosity is its most important property.

Viscosity has a direct bearing on wear protection, and your engine is designed to operate best using a motor oil of a specific viscosity (e.g. 5W-30).

The intense pressure the oil bears as it’s squeezed between moving parts, like the piston ring/cylinder wall interface, can tear apart, or shear, its molecular structure, leading to viscosity loss.

Suddenly, the 5W-30 motor oil your engine was designed to use is now essentially a 5W-20 oil, and wear protection may be compromised. When this happens, it’s time to change your oil.

Shop AMSOIL Synthetic Motor Oil

Fuel dilution

Fuel can wash past the piston rings and contaminate the motor oil, causing it to lose viscosity.

Frequent short trips that don’t allow the oil to reach normal operating temperature can be especially problematic because the fuel won’t volatilize and exit through the PCV system.

Excessive fuel dilution leads to sludge and varnish, requiring you to change oil more frequently.

Additives: designed to deplete

Additives are added to base oils to reduce destructive processes and enhance beneficial properties.

For example, antioxidant additives help slow the rate of oxidation. Detergency additives help prevent deposits and sludge while cleaning pre-existing deposits. Formulators add anti-wear additives to some lubricants to form a sacrificial barrier on metal components and help prevent wear.

Since they’re sacrificial in nature, additive depletion is one of the primary reasons motor oil loses its effectiveness and must be changed. 

While AMSOIL synthetic motor oil gives you the convenience of fitting oil changes into your schedule, it remains vital to install fresh oil at the appropriate time.  

Shop AMSOIL Synthetic Motor Oil

Motor Oil Viscosity Explained

Dual-Clutch Transmissions (DCT)

How Does a Dual-Clutch Transmission (DCT) Work?

John Baker | Jan 02, 2020 11:43 AM

A dual-clutch transmission (DCT) is synonymous with high performance. Compared to a traditional automatic transmission, it delivers…

• Faster, smoother shifts
• Increased fuel economy
• Improved performance

Although the DCT transmission dates to the 1930s, it made its first practical appearance decades later in several 1980s-era race cars.

In 2003, the Volkswagen Golf Mk4 R32 was the first production vehicle to feature the technology.

Today you can find a DCT in a variety of cars, from the relatively tame Hyundai Sonata to the brash, sexy Nissan GT-R.

How a DCT transmission works

DCTs are essentially two manual transmissions working in tandem.

One gear shaft contains the even-numbered gears, and the other contains the odd-numbered gears. While you’re accelerating in first gear, for example, the computer selects second gear on the other gear shaft. When it’s time to up-shift, the clutch that controls the even gears disengages and the clutch that controls the odd gears engages.

Compared to a traditional automatic transmission, gears shift much more quickly and smoothly in a DCT transmission – the perfect complement to a powerful, high-performance engine.

While DCTs are capable of seamless shifts, they can suffer from shudder or lurching at slow speeds.

Transmission fluid with specific frictional properties is required to prevent shudder. DCT fluid must also maintain the proper viscosity to provide protection during the high-heat operation native to high-performance sports sedans and supercars.

Buy AMSOIL DCT Fluid

Protect the thrill

AMSOIL 100% Synthetic DCT Fluid is specifically engineered for sophisticated dual-clutch transmissions.

Its superior frictional properties protect against shudder and gear clashing to consistently produce fast, smooth shifts.

AMSOIL Synthetic DCT Fluid’s exceptional durability provides stability in stop-and-go traffic and excels under intense, high-heat conditions. Its built-in oxidation resistance helps prevent sludge formation in vital transmission parts.

Look up your vehicle

For more information on AMSOIL DCT Fluid click here.

For more information on AMSOIL Synthetic Lubricants click here.

New ILSAC GF-6A & GF-6B Motor Oil Specs For Modern Engines

ILSAC GF-6 and API SP specifications coming May 1. 

AMSOIL is already ahead of the game.

Original equipment manufacturers (OEMs) are under pressure to improve fuel economy and reduce emissions. As a result, most new engines today use some combination of turbochargers, direct-fuel injection and variable valve timing to deliver better fuel economy and increase horsepower. The trend of lighter engine oils to achieve these goals continues with 0W-16 viscosities emerging in the market and 0W-12 and 0W-8 expected to follow. The industry has responded to these ultra-light viscosities with two new oil specifications: ILSAC GF-6 and API SP.

We Are Already There

Our claims about using advanced technology aren’t just talk, and this specification update proves it. AMSOIL synthetic motor oils already meet or exceed the new industry standards and require no change in formulation. This is not the first time we’ve been in this position. While the competition works on making major formulation adjustments, we just have to update our labels. The new specifications are not allowed to be displayed on labels until May 1, 2020. Expect to see updated AMSOIL labels then.

The Big Split

The International Lubricant Standardization and Approval Committee (ILSAC) recently set a new precedent in the passenger-car motor oil market by splitting its specification into two parts: 

GF-6A – backward compatible, provides protection for a variety of older and newer engines.


GF-6B – not backward compatible, for use in select new vehicles. 

Both versions focus on wear protection, prevention of lowspeed pre-ignition (LSPI) and improved engine cleanliness. However, GF-6B features a more stringent fuel economy test. Engine oils can easily be identified as ILSAC GF-6A or 6B by the API emblem on the front label of the packaging. A shield will represent the GF-6B specification, while the traditional starburst will indicate a GF-6A product. Both ILSAC specifications meet the industry-standard API SP specification which is most commonly found in owners’ manuals. 

To learn more, visit amsoil.com/lspi
 

What to do when a lawnmower won't start

Lawnmower Won’t Start? Do this.

A lawnmower that won’t start, especially when taken from storage, is almost always due to one problem: bad gas.

Storing a lawnmower in the fall without adding gasoline stabilizer to the fuel tank can cause the fuel to break down and plug the fuel passages. If fixing that problem doesn’t help, there are a few other common maintenance practices to try, as we explain below.

Here’s what to do when your lawnmower won’t start

Replace the gas

Over time (like the six months your lawnmower sat in your garage over the winter), the lighter hydrocarbons in gas can evaporate. This process creates gums and varnish that dirty the carburetor, plug fuel passages and prevent gas from flowing into the combustion chamber.

The carburetor bowl below formed corrosion and deposits during storage, which can easily plug fuel passages and prevent the engine from starting.

Ethanol-containing gas can absorb water from the atmosphere, which can lead to phase separation, which occurs when ethanol and gas separate, much like oil and water. Ethanol that has absorbed enough moisture and has sat long enough can foul the fuel system and prevent the engine from starting.

No matter how many times you yank the starter cord and pollute the air with your advanced vocabulary, the lawnmower won’t start if it isn’t getting gas.

In extreme cases, evaporation of lighter hydrocarbons can change the gasoline’s composition enough to prevent it from igniting. The gas may be fueling the engine, but it doesn’t matter if it won’t ignite.

If you neglected to add gasoline stabilizer to the fuel prior to storage, empty the tank and replace with fresh gas. If the tank is nearly empty, simply topping off with fresh gas is often enough to get it started.

On some mowers, you can easily remove and empty the fuel tank. Sometimes that’s more trouble than it’s worth. In these cases, use a fluid extraction pump or even a turkey baster.

Clean the carburetor

You’ve replaced the fuel, but your lawnmower still won’t start.

Next, try cleaning the carburetor. Remove the air filter and spray carburetor cleaner into the intake. Let it sit for several minutes to help loosen and dissolve varnish and gums.

On some carburetors, you can easily remove the float bowl. If equipped, first remove the small drain plug and drain the gas from the bowl. Remove the float bowl cover and spray the float and narrow fuel passages with carburetor cleaner.

This kind of “quick-and-dirty” carburetor cleaning is usually all it takes to get the gas flowing again and your lawnmower back to cutting grass.

If not, consider removing the carburetor from the engine, disassembling it and giving it a good cleaning. Be forewarned, however: taking apart a carburetor can lead to nothing but frustration for the uninitiated. Take pictures with your phone to aid in reassembly. Note the positions of any linkages or the settings of any mixture screws, if equipped.

If you’re at all reluctant, visit the servicing dealer instead. Also consider replacing the carburetor altogether. It’s a fairly simple process on most smaller mowers and it’s often less expensive than taking it to the dealer.

Clean/replace the air filter

With the air filter removed, now’s the perfect time to clean it. Tap rigid filters on a workbench or the palm of your hand to dislodge grass clippings, leaves and other debris. Direct compressed air from the inside of the filter out to avoid lodging debris deeper into the media.

Use soap and water to wash foam filters. If it’s been a few years, simply replace the filter; they’re inexpensive and mark the only line of defense against wear-causing debris entering your engine and wearing the cylinder and piston rings.

Check the spark plug

A dirty or bad spark plug may also be to blame. Remove the plug and inspect condition. A spark plug in a properly running four-stroke engine should last for years and never appear oily or burned. If so, replace it.

Use a spark-plug tester to check for spark. If you don’t have one, clip the spark-plug boot onto the plug, hold the plug against the metal cylinder head and slowly pull the starter cord. You should see a strong, blue spark. It helps to test the plug in a darkened garage. Replace the plug if you don’t see a spark or it appears weak.

While you’re at it, check the spark-plug gap and set it to the factory specifications noted in the lawnmower owner’s manual.

If you know the plug is good, but you still don’t have spark, the coil likely has failed and requires replacement.

Did you hit a rock or other obstacle?

We’ve all killed a lawnmower engine after hitting a rock or big tree root.

If your lawnmower won’t start in this scenario, you probably sheared the flywheel key. It’s a tiny piece of metal that aligns the flywheel correctly to set the proper engine timing. Hitting an immovable obstacle can immediately stop the mower blade (and crankshaft) while the flywheel keeps spinning, shearing the key.

In this case, the engine timing is off and the mower won’t start until you pull the flywheel and replace the key. It’s an easy enough job IF you have a set of gear pullers lying around the garage. If not, rent a set from a parts store (or buy one…there’s never a bad reason to buy a new tool) or visit the dealer.

My lawnmower starts, but runs poorly

If you finally get the lawnmower started, but it runs like a three-legged dog, try cleaning the carburetor with AMSOIL Power Foam. It’s a potent cleaning agent designed to remove performance-robbing carbon, varnish and other gunk from carburetors and engines.

AMSOIL Power Foam Carb Cleaner

Add gasoline stabilizer to avoid most of these problems

Which sounds better? Completing all these steps each year when your lawnmower won’t start? Or pouring a little gasoline stabilizer into your fuel tank?

Simply using a good gasoline stabilizer can help avoid most of the problems with a lawnmower that won’t start. AMSOIL Gasoline Stabilizer, for example, keeps fuel fresh up to 12 months. It helps prevent the lighter hydrocarbons from evaporating to reduce gum and varnish and keep the fuel flowing. It also contains corrosion inhibitors for additional protection.

AMSOIL Gasoline Stabilizer

I have a five-gallon gas can in my garage from which I fuel two lawnmowers, two chainsaws, two snowblowers, a string trimmer, an ATV and the occasional brush fire. I treat the fuel with Gasoline Stabilizer every time I fill it so I never have to worry about the gas going bad and causing problems.

You can also use AMSOIL Quickshot. It’s designed primarily to clean carburetors and combustion chambers while addressing problems with ethanol. But it also provides short-term gasoline stabilization of up to six months.

Sludge or Slime in the Radiator

 What causes radiator sludge/slime and what can you do about it?

• Additives dropping out: Coolant consists of a base (typically ethylene glycol or propylene glycol) mixed with additives and water. The base is primarily responsible for providing freeze and boil-over protection. The additives guard against corrosion, cavitation and scaling. Mixing of incompatible coolants can cause the additives to “drop out” of the solution and form sludge or slime.

• Contaminated coolant: A bad head gasket or cracked cylinder head can allow oil and coolant to mix, resulting in sludge. In vehicles with automatic transmissions, the engine-cooling system also cools the transmission. A breach in the system can contaminate coolant with transmission fluid.

• Corrosion: Occurs when an imbalanced coolant chemically reacts with metallic surfaces, forming reddish deposits that can appear as sludge or slime. 

Low-quality coolants can lead to cooling-system corrosion.

Performing fluid analysis is the only way to definitively identify what’s causing sludge/slime in your radiator. The report can identify oil, transmission fluid or other contaminants in the coolant.

Fix any mechanical defects and flush the cooling system. Refill with a high-quality antifreeze/coolant.

What kind of coolant should I use? 

Let’s start with what kind you should avoid.

You’re no doubt familiar with the conventional “green” coolants found at most retailers due to their low price. They contain inorganic salts, such as nitrites, phosphates and silicates.

Inorganic salts deplete quickly – typically in two years or less – and are on the environmental watch list. Once depleted, they are the source of common cooling-system problems, like scale deposits and sludge/slime.

Low-cost “green” coolants are the source of several problems, such as radiator sludge/slime and scale deposits.

For these reasons, most vehicle manufacturers have moved away from inorganic salts. 

And so should you. 

Instead, use a high-quality coolant that uses organic-acid technology (known as OATs). OATS coolants are much more robust and longer-lasting. They virtually eliminate drop-out, scaling and compatibility issues inherent to inorganic salts. This type of coolant can be used in a wide variety of applications, even mixing with other coolants as a top-off. 

AMSOIL Antifreeze/Coolants

AMSOIL offers three coolants, all of which offer a unique blend of organic acids. We use di-acid technology, which means both ends of the organic acid are active. This makes them work faster and form stronger bonds for enhanced protection. 

AMSOIL Passenger Car & Light Truck Antifreeze & Coolant is formulated for all passenger cars and light trucks. It is premixed 50/50 with high-quality water.

AMSOIL Passenger Car & Light Truck Antifreeze & Coolant

AMSOIL Heavy-Duty Antifreeze & Coolant is dialed in for the unique needs of on- and off-road heavy-duty applications. It is also premixed 50/50 with high-quality water.

AMSOIL Heavy-Duty Antifreeze & Coolant

AMSOIL Low Toxicity Antifreeze and Engine Coolant is a 100-percent concentrate polyglycol formulation for situations that call for a low-toxicity product.

AMSOIL Low Toxicity Antifreeze and Engine Coolant

Zinc Wear Prevention in Motor Oil

Do Older Engines Need Oil With ZDDP Additives?

What is high-zinc motor oil?

Zinc dialkyldithiophosphate (ZDDP) is the most common zinc-based additive and is used primarily as an anti-wear agent to prevent premature engine wear. It also provides corrosion and oxidation protection.

However, because the zinc and phosphorus found in ZDDP can negatively affect catalytic converters, it has been phased out of motor oil formulations in recent years.

Reducing ZDDP has drawbacks, as classic-car owners have found. Older vehicles with flat-tappet camshafts and, in particular, engines that include high-tension valve springs or other modifications that create high contact pressures, can suffer premature wear due to reduced ZDDP levels.

For best protection, engine builders and gearheads typically use high-zinc and high-phosphorus motor oil to offer extra protection for flat-tappet cams, lifters and other components during break-in. AMSOIL Break-In Oil, for example, contains 2,200 ppm zinc and 2,000 ppm phosphorus.

Buy AMSOIL Break-in Oil

How do ZDDP additives work?

ZDDP anti-wear additives are heat-activated, meaning they provide wear protection in areas of increased friction.

As temperatures rise and surfaces come closer together, ZDDP decomposes and the resulting chemistry protects critical metal surfaces. When parts move during operation, any sliding or rolling motion takes place on top of or within the ZDDP anti-wear film, which reduces metal-to-metal contact.

Flat Tappet Lifters

This is especially important in engines with flat-tappet camshafts or engines modified to create more horsepower. High-tension valve springs, often used in racing applications, also increase the potential for cam wear and require additional ZDDP.

Flat-tappet cams vs. roller cams

The design of flat-tappet cams makes them especially vulnerable to wear. As the name indicates, the tappet – or lifter – is flat. During operation, the cam-lobe slides rapidly over the tappet, increasing friction and temperatures.

A thin oil film is the only barrier that prevents the lifter and cam lobe from welding together.

If the oil film fails or provides insufficient wear protection, the two components can eventually wear the flat-tappet cam and affect valve operation. Engine power and efficiency can decline if the flat-tappet cam cannot lift the valves enough to adequately charge the chamber for ignition or release exhaust fumes. Because most V-8 engines of the muscle-car era came standard with flat-tappet cams, the problem is especially prevalent to classic-car and hot rod owners.

Roller cams, on the other hand, are differentiated by rolling contact rather than sliding contact. Although costlier, roller cams are common in most modern vehicles and can be retrofitted into classic-car and hot-rod engines.

The role of piston rings

Even though Hugh didn’t ask about it specifically, I should also mention the importance of seating the piston rings during break-in.

Although a new or freshly honed cylinder appears smooth to the naked eye, it actually contains microscopic peaks and valleys. If the valleys are too deep, they collect excess oil, which burns during combustion and leads to oil consumption.

The sharp peaks, meanwhile, provide insufficient area to allow the rings to seat tightly. That means highly pressurized combustion gases can blow past the rings and into the crankcase, reducing horsepower and contaminating the oil.

Breaking in the engine wears the cylinder-wall asperities, providing increased surface area for the rings to seat tightly. The result is maximum compression (i.e. power) and minimum oil consumption.

Do you always need an oil with ZDDP additives?

Do you need to use high-zinc motor oil in an older engine after break-in, which is typically about 500 miles?

Yes, if you want to maintain horsepower and promote longevity. 

Even after the cam has seasoned, it’s still exposed to tremendous heat and pressure, especially in a heavily modified or racing engine. The constant barrage of pressure can rupture the oil film responsible for preventing wear, leading to metal-to-metal contact.

After break-in, we recommend using an oil with at least 1,000 ppm ZDDP in a flat-tappet engine. That way, you’re providing your expensive engine with maximum protection against wear and horsepower loss.

AMSOIL Z-Rod Synthetic Motor Oil, our primary recommendation for classic cars and hot rods, contains more than 1,400 ppm zinc and more than 1,300 ppm phosphorus.

Buy AMSOIL Z-Rod 10W-30 High Zinc Synthetic Motoroil

Buy AMSOIL Z-Rod 20W-50 High Zinc Synthetic Motoroil

That’ll keep your classic car running for the long haul.