496 mag. fuel

[bear down]

I have about 15 gallons of 50/50 race fuel/premium left over from glamis...Can I pump this gas into the boat and use it up or should I just dump it. Thanks

[phebus]

Dump it in the boat. It is just a higher octane fuel, and might soot up your transom a little because your motor is designed to run on 87 octane, and the higher octane won't burn as fast, but if you dump 15 gallons and then fill your tanks the rest of the way it should be neglible. With the cost of fuel, definately don't dump it.

[bear down]

Sweet...With the 50/50 mix I am at 100 octane and I figure mixing the 15 gallons of it with 35 of 87 should not be too bad...I just don't want to ruin any sensors or components!

[Kachina26]

Waste of good gas, but no harm to the motor. :coffeycup

[dicudmore]

I have been told that the race fuel CAN AND WILL be a prob w/the EFI :220v:

[Sandbar Junkies]

I agree a waste of good gas , it will probally run really rich.. You should run the 87 all the time that what your suposed to use in it, and will probally run the best.

[bordsmnj]

merc motors retard the timing a little when you run high octane gas. you get less hp out of the motor than if you ran straight 87. don't ask me how the motor knows but it does.lol -jas

[Havasu Hangin']

merc motors retard the timing a little when you run high octane gas. you get less hp out of the motor than if you ran straight 87. don't ask me how the motor knows but it does.lol -jas

I always thought that the ECU retards the timing when you run lower octane? Isn't that what the knock sensor does?

[bordsmnj]

some silly boat mag did a test to see if running premium fuel instead of regular cheap stuff helped merc motors designed for 87 octane.the results where what i posted above. BUT,i've been wrong before. it may not be the knock censor that does that due to fuel . i think there is a censor in or after the exhaust manifold that may know but that's a guess.

[Jeremy1Kanobe]

Definately use that fuel. It should not foul any sensors. EFI's only control over timing, assuming that the motor is warmed up and naturally aspirated, is from the knock sensor. When a motor begins to detonate(knock) the timimg will be pulled back until no knock is detected. When running a higher octane fuel the threshold for detonation is raised and therefore the knock sensor will not indicate the need to pull timing back. More advance timing=More power!