haley10, I agree that automotive oils can be improved upon when used in an air-cooled application ... with
MolaKule's SX-UP, Schaeffer 132 and a few other additives providing useful extra barrier protection.
However most of these engines are horribly neglected and ANY oil changed regularly would ensure a long, long useful life.
Having said that I use Schaeffer 15w40 in most of my power equipment. I'd like to see an lawn & garden OEM oil top their barrier anti-wear package.
In others, I often additivize with the aforementioned products as well as a little Red Line Oil.
But I
still say that most people would be perfectly fine using mass-market automotive oil changed regularly.
jef1ge, you won't find many here who think a 20W-50 is ideal for these engines.
MolaKule did an informal test a while back and found that the extra thick 20W-50 caused the engines to actually run hotter than a thinner oil.
Most of these engines are designed to run on a 30 weight oil. Some, like me, are big proponents of 15w40 oils in these applications (should be just a bit thicker at temp than a 30 weight) ... but I'd never go thicker than this unless the engine was a total basket-case on its last legs.
The main idea of going with the 15w40 is to get the excellent additive package and shear stability. The same lines of oils Delvac, Chevron Delo400 etc ... in 10w30 would be equally as fine as 15w40 (maybe even better!)
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Bror Jace