Quote:
Originally Posted by Cloud
still waiting for my car. In the meantime, however, I invite your comments on the best kind of oil to use.
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The difference is that conventional oil feature larger molecules. These were especially important because poorly machined engines contained lots of debris and blowby materials. Synthetic was only used in, for example, jet engines where the oil was not contaminated by burned fuel.
Larger oil molecules made the debris less destructive.
Machining to tenths of thousands of inches and other innovations made synthetics more practical. Oil that was once so fully contaminated in 4000 miles (or 500 miles in the 1950s) is now cleaner even after 8000 miles. So the advantage of larger molecules is no longer as significant.