PDA

View Full Version : 87 vs. 91 oct. fuel


jojoshow
05-19-2006, 05:31 PM
New 496ho that just got broke-in on 92oct. for appx. 7hrs. Just wanted to know if this will be a need in the future or does it really matter with this motor. Pretty sure the 496ho is in the neighborhood of 9:1 compression. Any thoughts out there? Thanx.
92562
05-19-2006, 05:42 PM
Mag & MagHO engines will actually dyno less HP with anything higher than 87. The computer is set up to run on 87 only. Resist the temptation and save your money for beer!
dicudmore
05-19-2006, 05:43 PM
as stated above...that engine is designed for 87 octane fuel. will gain nothing with higher octane and may actually run worse :wink:
Beer-30
05-19-2006, 05:45 PM
Ditto.
Yay, though, I don't know how the ECM would ever know what fuel was in it - I DO know that it is basically set up to run on water and higher octane has zero effect.
Pump the 87 through it till it quits!
It has a knock sensor, so even if you got some real low-grade juice, it will still protect itself. Don't sweat it.
NuckinFutz
05-19-2006, 06:27 PM
The other thing I've seen with my HO is if I run higher octane than 87 I get more black soot residue on my transom and we all know just how much fun that is.
Chromegorilla
05-19-2006, 06:38 PM
Everyone is right so far..... don't waste your money.... 87 only
Parker Dreamin
05-19-2006, 06:55 PM
great question asked.....I had no idea and have been running 91. Sounds like 87 will do the job.....
jojoshow
05-19-2006, 07:59 PM
thanx everyone thats good info.
257
05-19-2006, 08:43 PM
The other thing I've seen with my HO is if I run higher octane than 87 I get more black soot residue on my transom and we all know just how much fun that is.
when i got mine i ran 91 soot and called mercury and he said old school
big cubes run 91 said to run 87 only
voodoomedman
05-19-2006, 08:44 PM
Yeah I was being stupid and putting 91 in mine at first until I asked the same question. I also read the manual which states to use 87. I just wanted to protect my engine. But if it's rated for 87 that's all you need.
257
05-19-2006, 08:46 PM
i put on gibson mufflers and i have less soot and runs better
I DIG IT !
05-20-2006, 07:09 AM
would that be the same for a 2000 502 mpi ????
Beer-30
05-20-2006, 08:38 AM
would that be the same for a 2000 502 mpi ????
Not quite, but somewhat. It is still a fairly low-compression motor, with knock sensor. Shouldn't be a problem at all. I would.
sorry dog
05-20-2006, 10:19 AM
Last time I got 91 was when I put 2/3rds 87 and 1/3rd 93 in.