Fork oil and shaft drive oil

I'm looking to change the fork oil. The repair manual says to use SAE 5W20 oil.
Could I just use regular $2.50 motor oil, 5W30, instead of the $9.00 "fork oil" the motorcycle shop wants?
I also want to change the oil in the final drive(shaft drive). The manual calls for GL-5 SAE80w or 90W depending on temperature.
All I can find is 80W90 not straight weight. Is this ok?

Post edited by: jon0108, at: 2006/03/23 17:07

My Owners Manual says to have the fork oil changed by your "authorized Kawasaki dealer". Ha!
My Shop Manual calls out SAE 10W oil for the forks. Is that lighter than 5W20?
Anyway, higher-viscosity oil won't move thru the little orifices inside the forks as quickly, so the result should be a stiffer ride. Could be a problem if you're cornering on some bumps... the tire needs to stay on the road.

You will likely blow out your fork seals using car oil. Stick to fork oil... 10w or 15w. As far as the final drive oil, the multiweight will work just fine. 80W90 is good. It is also called hypoid oil at an autoparts store.

Aside from the viscosity diff of motor oil, I'm pretty certain that fork oil also has diff properties and characteristics that motor oil does not.
Motor oil is designed to not only lubricate, but to also withstand severe high temps, where fork oil is more similar to hydraulic oil and performs more as a "liquid cushion".

As far as oil for the final drive (shaft), you are ok in using a multi-grade oil. I'm using Spectro 80w90 (designed for motorcycles=$4.99 a quart) Hypoid gear oil.
I'd suggest just reading the recommendations on the bottle you're considering on getting to see if it's designed for motorcycle final drives, and make sure it's Hypoid gear oil.

Post edited by: RetroRiceRocketRider, at: 2006/03/24 16:03

which one should i use 10w or 15w? Which is closer to 5w20?

The closest thing to 5w20 is 5 wt oil, so 10w fork oil is probably close enough.