Motorcycle Repair: Oil Weight, yamaha fzr600, oil viscosity

Question
I have a 1995 Yamaha FZR600 (EXUP).  The manual recommends that I use 20W-40 oil, however, no other brand offers that weight except Yamalube.  The closest weights available by most brands is 10W-40 and 20W-50.  Which should I use?  I live in WI, but I'm not sure if that makes much difference as I do not ride when it is below 40F.

Thanks.

Answer
Hi Steve,

Kinda limits selection to Yamaha's own product. I think you'll be fine with 10W40.

The first number in the oil viscosity number "10W" means: flows like a 10 weight oil in cold temps. The "W" means Winter. The second number "40" means: protection of a 40 weight oil when warm.

Summary: flows like a 10 weight oil in winter when engine is cold and offers protection of 40 weight oil when engine is up to temp.

Oils marked "SAE40" means: they act like a 40 weight oil all the time, hot or cold. Makes for hard starting and sends batteries to their resting places in the cold winter.

Respectfully,
Mark Shively