Just use KOHLER 10-30 and call it good.
We use this oil in almost every commercial & homeowner unit that comes through our shop. Kohler did good with this oil and has it blended to withstand some pretty harsh environments Specifically Commercial use where the engines regularly see 50+ hours of run time per week..
The solid pushrods are pretty much standard for Kohler and require no special attention nor concern. While most Kohler engines run a metal cam, almost all of them run a plastic oil pump drive and governor gear. I have NO clue what the material is made of but it's [censored] durable, while we do governor assy's on Kohlers from time to time (they come apart) I've NEVER seen a bad Pump Drive Gear..
I've seen a LOT of Blown Up engines this year and all but one I attribute to the Owners lack of proper maintenance and OCI's..
IMHO the oil type is much less important/critical then a good maintenance schedule and proper OCI's.
BTW, anyone reading this DO NOT "assume' that STRAIGHT weight Oils are OK for ALL Kohler Engines. MOST of the current Kohler engines run Hydraulic Lifters and "REQUIRE" the use of 10-30 weight oil.
FWIW, I was at a Kohler school and there was some dicussion of the "COURAGE" engines (as there ususally is).. When the Rep asked those in attendence how Kohler got the Name "COURAGE"? One of the TECHS said "Because Kohler had the COURAGE to put their Name on it"..
I thought that was really funny..