Quote:
Originally Posted by ProDigit
Most 10W30 car oil does not have modifiers.
Thinner or thicker oil does.
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I don't believe that is correct.
Here's a photo of the back panel of Mobil 1 5W-30 and 10W-30 oils. Both say "Energy Conserving" at the bottom of the API "donut" - so they both have modifiers.
This is the API legend -
All oils in the 40-grade range (5W-40, 10W-40, etc) do not have modifiers.
But that's not the real reason not to use auto oils. The
real reason is the lack of adequate levels of ZDDP (Zinc and Phosphorus) that are required to protect the valve train in most cycle engines. Current auto oils have reduced levels of ZDDP in order to extend the life of the emissions catalyst - which is only adequate if the engine has roller valve trains.
Almost all cycle engines do not.
The answer for cycle engines are diesel oils like Rotella. They are generally a heavy duty base stock and have the higher levels of ZDDP that a cycle engines needs. No reason not to use them.