fwiw-
Retired now but my eldest Brother was designing Turbine Jet engines right out of college for Babcock in the mid 60's. He told me over 40 yrs ago when the Turbine jet engines were first tested they couldn't run long at all due to the heat cooking all the oil and they simply seized. It took a long while for the oil industry to catch up and develop an oil that could withstand the heat produced by the jet turbine engines. The oil they came up for the turbines was Synthetic oil. The military kept this oil technology under lock/key for many many years to keep other countries behind our jet engine development. It wasn't brought to the mass market until a fighter pilot brought it to market in early 70's as we now call Amsoil. (No affiliation at all here).
Regardless' what anyone ever tells you, any engine in a mower,tiller, gen etc.. will last longer for lack of oil breakdown using a full syn. Regardless of syn brand it still flows,cleans and protects better than any Dino oil can, besides its longevity is so much better. Maybe the higher Zinc oil Kohler offers can hold a candle for wear longer than other dino oils but only to a certain temp, but' then any Syn just walks all over it. Reason I doubt Kohler oil? 1st its Quaker State which has always been the lowest grade oils on the world's market, 2nd "What % zinc is actually in it?" It don't take much to say it has more Zinc than competitors when others have no zinc to speak of?... Same with Syn blend, now' is that a single drop of syn in a tanker load of dino? Unless its changed no law says it has to be anymore than a drop to say "blend" on a bottle. See that % in writing?
I've ran 10w-30 full syn in my Kohler Wheel Horses over 2 decades now without issue one, no smoke, never re-ring/rebuilt one yet. Most times Mobil 1 now days as its easy to locate, I ran Amsoil yrs ago. Keep in mind the manuals of yesterday's engines all say SAE 30 because locating full syn oil was very hard for any customer yrs ago, just wasn't used then. Understand too, Oil corps and engine makers have contracts to promote each others products so just beware these contracts may not end for yrs to come to even change recommended oils without lawsuits. Most likely their huge contracts never were in their consumers best interest when greed comes into play we all pay, do they really think of you? Look at your gas prices, same people...lol
Peace