Most of the automotive synthetic oils have an additive that WILL affect your clutch. If your losing mileage and it feels like your power is down you may want to change the oil back to the recommended oil in your manual. Don’t, I repeat, don’t tell your dealership. If their pricks they will use the synthetic automotive oil as an out.
You’ve probably messed up your clutch plates a little with what is “too good” of an oil, and lost some of the friction needed to operate your clutch. An oil change or two might just do the trick. Good luck.
TOTALLY disagree with this post! I've had CAR (NOT motorcycle!) Mobil 1 15w-50 in my Versys from about 3,000 miles to the present 8,150. NO problems!
Had a '79 Yamaha SR500 till my son bought it last year, and it was on Mobil 1 CAR 10w-30 as long as I had it. NO problems!
My '04 KLR has 49,665 kms (30,000 miles) and has been on CAR Mobil 1 15w-50 since 4,713 kms. NO problems!
I sold an '03 Suzuki Bandit 1200S (104 horsepower!!!) last summer with about 40,000 kms on it, and it had been on CAR Mobil 1 10w-30 since 4,000 kms. NO problems!
And when I say "NO problems!" - I mean NONE, not with the clutch, transmission (shifts WAY better on Mobil 1) or engine, AND I've used "extended" oil change intervals on all 4.
ALL my vehicles (and my lawnmower and snowblower) run CAR Mobil 1 with NO problems!