oil?

I use Mobil 1 diesel turbo oil. I think it is 15w-40. I figure if it will stand up to a turbocharger, it will work just fine in my air cooled KZ1100s. Never a problem in 16 years. When I lived in the UP of MI, the artic tundra, I used regular Penzoil 10w-40. It gets too hot in Texas to run regular oil in my bikes....chris3

I use Kawasaki S4 Synthetic 10w40, on the advice from a Kawi mechanic.
My engine revs sooooo much smoother with it in.
It is made for wet clutches.
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Ronkz650, I dont know how long you go between oil changes but Ive been using Catrol 20/50 GTX for 35 years since my first Z1 and never have seen what youre talking about and never had an engine problem, including a solid year of drag racing the first Z1 every weekend and racing my current 1105 motored KZ1000

I always change every 2000 miles. The main thing that made me question the oil was every time I'd check the valve clearances the engine was clean as new. This was clear up over the 150,000 mile mark and it was burning quite a bit of oil by that time, but no problem. Then all of a sudden I see sludge, whithin 15,000 miles of there that's all there was. So in 15,000 miles the engine went from perfectly clean to 100% sludge. My theory will always be in the SA, SB, SC ratings somewhere along the road it went to S(crap). Something they add either for emissions and/or "better or additional" additives would no longer work in an air cooled engine with moderate to heavy blowby. So that is my theory of GTX personally, probably 100% wrong too.

I've just changed to the Rotella, sooooo silky smooth @ all RPMs. Plus, they have the gallons @ Wally World cheap!

I dont think Id complain about oil that went 150,000 miles in a bike myself. Id guess the problem was more that the motor was worn out. I dont go that long on oil changes, I have too many bikes to ride