So when i first got my pig i was running 91 octane because i thought it would be better than 87. But then i got to thinking with a 8.3 compression ratio it would probally make more power on 87. I tried the lower octane and sure enough it DID make more power. I have been running 87 ever since. As stated in another thread the temperature dropped recently and my bike lost a little power. Today i checked my tank and it was about half way up with 87 octane. I had a jug of 91 octane sitting around for my street bike. I topped the xr's tank with the 91 and shook the bike to mix the 2 different octanes togeather. Took the bike out and the lost power due to the colder weather was back as strong as ever. I dont get it??? Can someone tell me what happened???