I have a lawnmower with a 20 HP Kohler Command twin cylinder engine. This isn't an old engine, but I wanted to use synthetic oil in it . I talked to my local Kohler repair person on three different occasions and according to him it was discussed at a regional meeting (inservice) with other Kohler techs. He claims that the synthetic oil allows the engine to warm up too rapidly and that this detracts from proper engine operation because of varying rates of expansion and contraction. Components need to warm up gradually and with more uniformity than synthetic oil allows. I trust this gentlemen; he has a long-established business with an excellent reputation, his work for me has been outstanding, and he seems to be knowledgeable about all aspects of Kohlers, but I really wonder about this reason. This does not seem like a valid reason to use petroleum-based oil. It seems more like the kind of response I used to get from Ford and Chrysler--"The company has not tested synthetic oil and therefore does not recommend its use." Another interesting statement from the Kohler people is that 10W-30 oil is to be used instead of straight 30W because the additives are necessary to properly lubricate the overhead valves. Huh? Well, maybe, OK, hmmmmmmmm. I'm just the owner; I didn't design the engine.
