Reelthing wrote on 08/21/08 at 20:05:03:spose I can later - you posted 8 of the 1000's out there - was really just curious if these were the run of the mill - base every thing on comp ratio - that isn't near the whole story, water vs. air cooled, head metal, seasonal blends of fuel, and of course seasonal temps
Okay, okay. To summarize, an engine cannot use a higher octane gas than it was designed for, assuming you have it correctly tuned, and assuming you have not raised the combustion temperature by running the engine too hot. Example: if the fuel mixture is too lean, then the combustion temp will be hotter than it was designed to get, and you will experience pinging/knocking. Higher octane will help alleviate that problem, but the solution is to adjust the fuel mixture correctly. Or, if you idle your air cooled engine too long stationary, the engine will overheat and the combustion temps will raise too high, and you get a lean condition. Or, if you insist on lugging all the time, you may get the pinging/knocking and the higher octane will help that. Or, if you have your timing advanced too far, again the higher octane will help alleviate the pinging. So, unless you have a lean fuel mixture or a timing or overheating issue, or the combustion chamber is fouled with glowing red carbon deposits, a stock engine will see no power difference using a higher octane than the manufacturer recommends.