Octane

[Beefer]

I can get non-ethanol gas locally, with a 93 octane. Is the high octane ok for my 1984 MerCruiser 488r?

 

[drrpm]

Re: Octane

Octane basically is an indication of the gasolines resistance to premature ignition. Lower than specified octane will make then engine more likely to knock due to premature ignition. Higher than specified octane will have no effect other than being more expensive.

 

[Silvertip]

Re: Octane

Said another way, if your engine exhibits detonation/preignition even when properly tuned, then higher octane will help. If not, it only helps drain your wallet.

 

[Brewman61]

Re: Octane

Same here. My engine runs just fine on plain old 87 octane, but all of that stuff has 10% ethanol. The only ethanol free gas around here is premium- so I run that to avoid the alcohol. Boat runs just fine on the premium, and I get some peace of mind on the ethanol. Costs almost a buck a gallon extra.
Over a buck more if I fill up on the water.

 

[Beefer]

Re: Octane

Ok, that's what I thought. I can get non-ethanol from the marina at $4.10/gal 90 octane. There are 3 gas stations around here that sell non-e10, and one (the closest) only has it at 93 octane. The gas stations are running about $3.29/gal. If the 93 is ok to run, I may use it just for the convenience. Even $3.39 is a savings over $4.10. Thanks.