From what I read, the difference might be- meaning that I read it on the internet... that motorcycle oil has more zinc in it than ATV oil does, and ATV oil is designed for a wet clutch and centrifugal clutch operation, where motorcycles just have wet clutches. But, proof is in the pudding.
if you ever worked on a motorcycle motor ?, you will notice they both have a change clutch ?, they operate pretty much the same way, the only difference is the centrifugal clutches, motorcycles are set up a tad different ?, but they still operate off a wet clutch, which is pretty much the change clutch. I've been running 4-stroke motor oil made for motorcycles in my atvs for a very long time, and they run great !!, not once have I had trouble with my clutches slipping ? .

. as I said, its a name and price thing, both do the same thing

. what you can not do ?, IS RUN AUTOMOTVE OIL IN MOTORCYCLES AND ATVS !, THIS IS A NO NO !. now, you can run automotive oil in a 4-stroke motorcycle and atv engine, sure, it will operate good on the motor itself, piston rings, cylinder, gears, all that is ok ?, but where it fails is ?..IS ON THE CNETRIFUGAL CLUTCH, AND THE CHANGE CLUTCH !, it will make the friction disk in the change clutch slip, and make the centrifugal clutch arms slip in the bell housing ?, which will burn them up in a short time period. I don't care what the internet says ?, I know what works, and what does not

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