My Dealer here in Lafayette La says Kawasaki recommends 20/50 also.
I'd like to know myself. I will say that modern day API SN 10w40 and 20w50 oils are more shear stable than than they used to be.
My dads 27hp Kawasaki has right at 600hrs using 10/30 and doesn't use a drop of oil.
My FX1000V 35 hp Kawasaki has never used a drop of oil and I use straight 30 wt. Kohler oil, but like anything else, all engines can be a little different.
If it is that old I would not change what I have been doing.
I asked a Kawasaki rep at Expo this very question. His answer was the new oil recommendations are for all air cooled v twin engines.
Probably just wasn't used much.If it is that old I would not change what I have been doing.
Still, after 20 years if it ain't broke, don't fix it.
EPA emissions mandates have continued to go up. As a result, engine manufacturers continue to run them leaner and leaner, causing higher and higher operating temps. The heavier oils hold up better at the elevated operating temps.
