Gas Question

[paulsibek]

I've been using 91 octane and someone said they were using 89, my mechanic said 89-91.

Any thoughts?

[breyfogle]

IMHO, 89 is fine. That's all I have used for years.

[srb]

stay at or above minimum reqs. if the reqs say 89 there is not benefit to 91, unless that's all you can get.

[PGlaves]

Depends on what K model.

My 86 K75 was said by BMW to only need regular. We have had 6 K75s and they all ran fine on regular fuel.

I had a K1100 that also ran fine on regular. I'm not sure what the K1200LT and RS require. Look at the owners manual. BMW virtually never understates the need. If they say 89 - 89 is fine and 91 will do no real good.

[soldemall]

Also note that the Europeans calculate octane differently than we do, and arrive at a higher number. Don't have access to my owner's manual now, but there is a footnote to that effect. 89 there is 87 here.

I've never used anything but 87 on my '92 K75, and have had no issues with pre-ignition.

[PHMarvin]

Also note that the Europeans calculate octane differently than we do, and arrive at a higher number. Don't have access to my owner's manual now, but there is a footnote to that effect. 89 there is 87 here.

I've never used anything but 87 on my '92 K75, and have had no issues with pre-ignition.

Hi, All,
It's not that Europeans calculate octane ratio differently, it's that in the US, our government has decreed the octane number on the pump will be the sum of the research octane number and the motor octane number divided by 2. That's why you see (R+M)/2. 91 Research Method (ROZ in BMW-speak) equates to approximately 87 "pump" octane. In my K1100LT owners manual, it says minimum requirements are 95 octane (Research), 85 octane (Motor) or 89 octane (R+M)/2. Likewise, the book recommends regular (leaded or unleaded) for the K75. I have never had any of the K-bikes I've owned ping on regular unleaded fuel. This included a couple of thousand miles in Mexico in 1997 with my (recently sold) '96 K1100LT.