Originally Posted by Shreddin Rubber
Stay clear of any oil stamped energy conserving or resource conserving. They MAY cause you clutch to slip.
Actually, most car oils *are* now different, ever since the API SH standard came out (they're up to SM or SN now, IIRC). SG is the last oil type (now discontinued) that was safe for both cars and bikes. Most everything after that has reduced anti-wear additives (not good for your engine or trans on a bike) and friction modifiers to make up for this (which poisons your clutch and causes the slip), all in the name of reducing emissions and increasing fuel economy, engine longevity be damned. While the energy/resource conserving label is a dead giveaway on a non-JASO-MA rated oil, it isn't on all the ones that can shorten your bike's life and poison the clutch. There are car 20W50s out there that don't carry any sort of "conserving" label that *will* poison your clutch.
Diesel oils are now different, too. They couldn't get the newer eco-oils to work in a diesel so they mostly have left that standard alone. So if you have a diesel vehicle, you can't use 'car' oil either - not without damaging your engine.
The safest way to go is with a motorcycle specific oil or one that is JASO MA rated. (There are other JASO ratings other than MA and MB - MA/MB are for motorcycles, the other ones aren't.) Interestingly, motorcycle-compatible oil looks an awful lot (chemically) like diesel oil. Turns out they can be and often are the same - which is why Shell decided to run their Rotella T through the JASO certification for bikes, and is now busily selling the crap out of their product to both diesel owners and bikers. I suspect Chevron may be next to run their Delo oil through so as to compete.
In fact, if you have an older (pre-95) car that you'd like to keep, you may want to run it on diesel oil as well - it has the anti-wear additives that will keep it going longer and doesn't sacrifice anything for the eco-bullcrap.