This topic comes up a lot about these engines. In the end, most recommend to run the kohler 10w30 as it has a different kind of anti foam agent, or more of it, or something. I personally am using castrol Tection 15w40 because for some reason i am against buying OEM branded oils of most any type and i got it on sale for about 5 dollars a gallon a while back. I posted about the anti foam properties of HD or VII free oils a week or so ago and it didnt get much attention. Most guys that i have talked to on here about this say that most all modern oils have anti foam additives, but many have said that the Kohler branded oil did help there valve noise. Kohler oil is not very expensive, maybe try it and see if it helps. I have a command 20hp Vtwin and it has run on Mobil 1 5w30 and 10w30 up until last summer when i started using the tection. I honestly thought the 15w40 ran a little quieter last summer but as i just cut grass yesterday, i think it is about the same. I has some valve noise but nothing terrible and it may be normal. Im probably gonna try some M1 5w40 as i have about 6 qts in my stock pile of cheap oil that needs used up. I was going to use my castrol Edge 10w30 but it is on the thin side and these engines are on the hot side so it just dont feel right to me. I think the rotella 10w30 would probably do as good as anything in there but just for fun maybe try the kohler oil. Good luck, let us know what you do and how it works out.
