I will be honest on this one, I do not know the compression ratio on this motor. The bottom end was built when I bought it and even though I went through and checked the bearings years ago, I did not try to measure the specs to get the CR calculated, I have always thought the 114 octane would be a safe bet, but I might just experiment with some lower octane to see what the results are. Certainly at $11-$12/gallon I do not want to buy gas more expensive than I need!
I will put getting the CR figured out on my list of things to do. Thanks.