The GS uses a wet clutch, meaning the clutch is immersed in engine oil. That's why oil choice affects the clutch. Synthetic oil is super slick - great for the engine, but makes the clutch's job more difficult. Kevlar based friction plates are made to work in a synthetic environment, standard cork based friction plates are not. Many people claim their stock clutches hold up just fine in synthetic providing you make the switch to synthetic early in the clutch's life. In my opinion, based on my personal experience, full synthetic is a bad idea with a cork based clutch (like your stocker). A synthetic blend, like Motul, would probably be a good compromise if you're looking for the benefits of synthetic without risking the clutch.

I just did an oil change and I used Shell Rotella T - bike loves it!

Quote from: octaneThe GS uses a wet clutch, meaning the clutch is immersed in engine oil. That's why oil choice affects the clutch. Synthetic oil is super slick - great for the engine, but makes the clutch's job more difficult. Kevlar based friction plates are made to work in a synthetic environment, standard cork based friction plates are not. Many people claim their stock clutches hold up just fine in synthetic providing you make the switch to synthetic early in the clutch's life. In my opinion, based on my personal experience, full synthetic is a bad idea with a cork based clutch (like your stocker). A synthetic blend, like Motul, would probably be a good compromise if you're looking for the benefits of synthetic without risking the clutch.

so what happens to the clutch when its immersed in super slick oil?  how does it affect its operation?  just curious...


- alex

MMMMMM Rotella... tastes great on ice cream and easily adds 40 HP to the bike....

The purpose of oil in a wet clutch system is to cool the friction plates - not for lubrication as is it's purpose in the engine. Oil with better lubricating qualities is good for an engine, but will often cause the friction plates to slip in a clutch. That slippage is what you feel when you ride a bike with a slipping clutch. The more worn the friction plates are when you introduce synthetic, the more likely they are to slip - unless you're using kevlar friction plates which are designed to not slip in synthetic.

The slip usually starts gradually and will get worse over time - sometimes over a very short period of time. When mine started slipping the bike felt normal when riding casually, but if I grabbed the throttle at any rpm in any gear, the motor would wind up and it would take a few seconds for the clutch to grab and move the bike. I'm not talking when I released the clutch - I mean with the clutch engaged and in gear. If the friction plates don't create friction and grab, the engine shafts will spin up with the motor, but the clutch won't be able to transfer the power to the drive sprocket.

Why use synthetic oils that were designed 30 years later than the engine was. Just use 10-40 keep it on the cheap. Replace oil sooner than recommended, keep up on maintenence, and your bulletproof suzuki engine will run as long as you let it.

Extra-virgin olive oil....of course, this works best in Ducatis, Moto-Guzzis, and some Vespas.

A wet clutch will run into problems with any oil (syn or dino) that is labelled "energy conserving".  These tend to be anything in the xW-30 range.  They've got a high level of friction modifiers that cause the problems octane is talking about.

Synthetics like Mobil 1 15W-50, 5W-40, or any of the motorcycle-specific synthetics will not cause any problems for your clutch.  The 15W-50 (some call it "red cap" due to the bottle) is one of the most popular oils for bikes of all kinds - if it made even a small % of clutches slip this would not be the case.

Use anything that fits what it says in the owner's manual.  10W-40 is the standard suggestions (as it's printed right on the dipstick) but there's plenty of other options depending on the climate and whatnot.  

jeff