For me it was never about extending drain intervals, but avoiding running the engine on bad/spent motor oil. Back in the early 1980s I did lube analysis on used motor oils on my car and others. There were no synthetics at that time and I was unable to find AMSOIL. Conventional oils of that era always flunked the lube analysis at 3,000 miles. The lab would recommend changing the oil and filter.
But my question was ..how long had that oil been bad? Seems the oils of that era passed, barely, at 2,000 miles. I was changing oil every 2,000 miles and my engines seemed to hold up sludge-free. Later when I discovered AMSOIL, I was skeptical of that 25,000 mile or one year drain recommendation. I pulled some used oil samples on AMSOIL lubricated cars that had gone the 25,000 miles. To my shock the samples passed with extra quality the conventional oils did not show at 2,000 miles! How was this possible? The base oil of AMSOIL did not degrade and contribute to the demise of the oil. Plus the better filtration of the AMSOIL oil filters kept oil much cleaner.
This video is more "scientific" than what I did, but proves the longevity of the oil and the extra longevity of the engine. All of this testing was done in 3rd party accredited labs outside of AMSOIL's influence. AMSOIL is so much better than other oils that often it's hard to comprehend.
