What Octane to use on 496?
 

I always like err on the side of safety (better oils, filters etc...) This is only my 2nd season as a boater, and will be my first full season. I've been filling up with nothing but 92 octane on a 100% stock plain 496 (375hp). Am I just pissing away money here? Seems to me with detonation/piston design issues with this motor it just seems safer. Also are their knock sensors on these things?

Would appreciate everybody's opinion on this.

TIA!

Re: What Octane to use on 496?
 

Do not use 92! The motor/computer is designed to run on 87. They don't like 92. You are definitely pissing money away.

Re: What Octane to use on 496?
 

Yes you are pissing away money! And I bet there is soot on your transom to boot.

Use the recommended 87, save money and give the computer what is was designed for.

Re: What Octane to use on 496?
 

No excess soot at all on the transom. How would the 92 octane gas be bad for the computer?

Re: What Octane to use on 496?
 

WOW, this feedback is an eyeopener. How does 87 octane fuel burn faster than 92? I'm confused.

Re: What Octane to use on 496?
 

The basic concept is that the higher the octane the more resistent to burning the fuel is, thats what the octane rating is all about. If you run a fuel that burns slower then a motor is setup for it may not be able to componsate the timing and injector pulse width adequatly within the preset perameters in the ECM.

Re: What Octane to use on 496?
 

I use 87 in mine, no problems. That's what Merc says to use.

Re: What Octane to use on 496?
 

I am surprised at that. My transom goes black when I am forced to put 92 in. We convinced my marina to start carrying 87 instead of 89 for this reason. I noticed a difference even then.

Re: What Octane to use on 496?
 

Use 87 octane like Merc says .

Saw something in Hot Boat mag a few years back where they ran a dyno on an 502 EFI . They ran 92 then 87 and saw HP go down with the higher octane . Had something to do with the computer making adjustments for the higher octane .

Re: What Octane to use on 496?
 

Thanks a bunch guys! :D I will be filling up with 87 from now on.

BTW, does the 496 MAG have a knock sensor that automatically retards timing if knock is present?

Again thanks for all the great feedback.

Sebastien