I use extra virgin olive oil.

I call bull, CL. There hasn't been a virgin this side of middle scool/junior high since 1977.:D

Clean oil
 

All that really matters is it meets the spec and is clean. It doesn't matter how much you spend if its not changed at regular intervals.

My BMW 750 that I have had for 21 years I run diesel 15W 40 (rotella or similar)
In my BMW 1100 with 123,000 miles on it, I use synthetic 15W50 I buy by the case at NAPA for $2.99 a quart.

In my KLX250SF I use mineral 10W40 and change it every 1500 to 2000 miles. Its up to 3400 miles. Once it hits 5,000 I may switch to the 15W 50 synthetic. I don't know how much this affects the clutch.

Oil breaks down by the temp it runs at. We have water cooled bikes, so its not much of a big deal. Just keep it changed.

David

I ran conventional rotella in my zx6r with over 40k street miles and not one problem. Sold it with the stock clutch still in it. and i beat the ever loving **** outta it. Rotella FTW!!!!

I always choose 5w-40 over 15w-40 cause the 15 weight oil is alot heavier and harder to carry to the checkout.

Castrol GPS- since first service. Part-synthetic. No probs!

Good call.
That's why I only run 10 lbs in my tires. The bike is too heavy, and doesn't handle right with 20 lbs.