Oil "without car-type additives"
 

I'm not quite sure where to put this question, but I'll try it here:

My "other" bike has a wet sump, meaning that the engine and the gear box shares the same oil. Someone on the net adviced me to use semi-synthetic oil on this bike. But, they prompted, the oil should be "without car-type additives". This being a while ago, I can't recall where I heard this advice and - more importantly - hence can't get them to explain what, exactly, these car-type additives are. Are there any semi-synthetic oil 5W-40 / 10W-50 without car-type additives readily available on the market? Anyone in the greasy business who might know what this is supposed to mean?

Take care!
indu

Car oils have an additive to increase fuel economy. I can't remember what they are. A bike with a wet clutch this type of oil can cause the clutch to slip. thumpertalk.com has discussed this several places on the drz-400 forum. Probably on other forums as well. It does not mater if it is regular oil, synthetic, or a mix this type of aditive can cause this problem. I use mobil 1 synethic for motorcycles without any problems.

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John

[This message has been edited by ekaphoto (edited 23 February 2004).]

Many motorcycles have wet clutches, and all that do will be at risk of having their friction material contaminated by the anti-friction additive present in car oils. Motorcycle oils don't have this, so you should always be fine if you use an oil specifically designed for use in bike engines. That said, bike oils are damned expensive, and I do quite high mileages (3,500 + miles a month) even when I'm not travelling, so I usually use car oils because they're cheaper. I had clutch slip on my previous two Transalps, but much of this was due to wear of the friction plates. The rest, I'm sure, WAS due to the oil because when I used car fully synthetic oil rather than mineral oil, it always made the slip worse.....

In short, stick to proper bike oils if you can afford to, and don't use friction modifying additives. If not (or if all you can get is car oils) go for car-spec stuff. My view is that I'd rather have an unworn engine with a slipping clutch than a knackered one with a healthy clutch.