Thats why I asked, I've been running regular, and the engine seems to be running great, but I noticed on the fuel tank that says use unleaded 90 octane and above. I'll run a few tanks of higher octane and see if I notice any different,
The compression is only 8.5 to 1 high octane is a waste of money at that ratio. Now if you boost it with a turbo or shave the head and get in the neighborhood of 9.5 or 10 to 1 then you will need high octane fuel to prevent preignition.