What octane for XR650L

Hello all, I have a question on what octane gas to run for my xr650l. I have run 93 octane in it since I got it (3000 miles ago). I was wondering what you all run and is it worth running 93..it is all stock except for the desnorkeling.

i definately notice a difference with supreme. its all i run

it says inside my left hand side cover on a label to use fuel with a 91 or higher octane rating

Hey tggray,

Any engine that has a compression of 9.5:1 or better should run 93 octane or you risk the possibility of detonation (knock and ping). I've seen holes burned completely through the tops of pistons due to prolonged detonation.:thumbsup:


Good thing the Ls are only 8.3-1 compression

i bumped my L up to 10.5:1 but I would use supreme on stock anyway, plus, it's a motorcycle, uses so little fuel!

I run only 87 in my R. Never had a problem.

Been running Shell 93 octane. I read someplace that folks should run premium on air cooled bikes if they can get it. The higher octane helps the bike to run cooler. For the few cents more per tank I figured why not?

It does not run cooler, however it does allow the engine to run hotter without pre-detonation. Octane it a combustion supressor. This allows the combustion pressures to be higher without damaging the piston. The hotter the engine, higher compression or advanced timing you run, the higher octane you need to run. It is a common miss conception that high octane fuel burns hotter. They believe that is why race cars run it. The air cooled engine has a greater chance of detonation since the only regulation of engine heat is air temp and flow. Reduce any of these and the engine can run hot.

You can run lower octane fuel, but will be at risk of detonation if the engine temps rise. I have run all grades at one time or another but try to stick with 92 and up (more so in the summer months).


my L just loves 87 Pemix out of the milk container...

no love here - :thumbsup:

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