Which Octane Fuel do you use ?

[Wake Havasu]

What can I use in a 6.0L GM?

[Tanner]

Anything that doesn't cause knocking or pinging. You should be able to run 87 no problem. If it causes problems then bump up to 89.

[dogbert]

Re: Which Octane Fuel do you use ?

Originally posted by Wake Havasu
What can I use in a 6.0L GM?

My dealer recommended mid-grade, so that's all I've been using. Occasionally, it's had premium when I couldn't get anything else. I would recommend using Stabil on a regular basis regardless of what type of gas you use.

[NICKYPOO]

I run 91 all the time. I began using it when it got really hot here (95+) and like the way it performed in the heat (higher octane = higher vaporization point) so I've kind of just stuck with it. Boat ran fantastic this weekend.

I have the Merc. 350 Mag so I guess I'll shut up now.

[Carter13]

My dealer said to run only 87 in our 06 22v. Evidently any higher octane causes the motor to run like s***. Something to due with the computer being unable to readjust the EFI. We've been running 87 and it runs very strong.

[Tanner]

Well the only problem I see w/ running a higher octane is the dent in your pocket. Although I guess it's possible that if you've been running a higher octane the whole time and step down from say 91 to 87 and the computer had adjusted for the "good stuff"... I guess it's possible you could get a bit of knocking. I doubt it though.

Your boat's motor isn't a supercharged or turbocharged engine w/ the timing severly retarded, so the higher octane isn't really needed.

[wrangler]

Interestingly, I used 87 the first tank with no problems... Thought to myself....self, if 87 is good, then 89 should be better right???

I contend that the boat ran better on 87. Smoother acceleration and overall operation... My next tank will be 87 again and we'll see if my theory is correct. The advice from the dealer is 87...so hey, why not...

[steves1967]

Being a drag racer as well as a Tige owner I can kinda explain the octane thing. The higher the octane rating the slower the explosion happens in the combustion chamber. On high compression race engines we want to be able to control the "explosion" or ignition of the fuel in the cylinders. 87 burns real easy so a hot spot on a piston can and will ignite the mixture prematurely..causing knocking and pinging- that is actually the "explosion" happening forcing the piston back down, but the crank and connecting rods are still mechanically forcing the piston up the piston rattles back and forth....bad deal. So with the high octane gas these hot spots on the pistons wont ignite the mixture.

So in theory, if you could have complete control over the cylinder and piston shapes, contures, and design-you would make more power with 87 because the flame travels faster....but in the real world i gotta pay $8.75 a gallon for 116 octane!!

[Tip]

I have the Merc 350 MPi and the manual says to use 87. I used to run 89 and 91 because it was the only thing I could get at the marina. While I was using the higher octane I noticed a black film on the transom. Every week I would clean the black film and rewax the transom, I thought it was a problem with the engine. A mechanic friend of mine told me that the black film is caused by running high octane in the Merc engine. I found this hard to believe but when I started running 87 octane the black film all but disappeared. Who knows? I do know that 87 is less expensive and the boat runs fine with it.

[Lucky 275]

Anyone running 87 in the 340hp Marine Power?

[CFord]

We're running 87 in the 5.7 L 340 HP Marine Power. Boat is nearly brand new (10 hours) and no problems at all yet.

[Lucky 275]

looks like that'll be what I put in my tank next. Thanks!

[NICKYPOO]

I ran 89 instead of the usuall 91 this last weekend and did not like it, or at least the boat didn't. It felt a tick week and didn't fire up nearly as quickly. With the 91 it's just a quick flick of the key and BLAP, she's a runnin'. Don't know if the 'puter was having trouble compensating or what but after a good solid year of 91, the Merc was a little upset with the 89. I guess it's spoiled.

[Tequilasun]

I run 89 in a 5.7 340 MP engine, no problems...

I have run a couple of tanks of 87, no problems...

[mtnsmith]

I run 87 in my 340hp Marine Power 5.7 in my 2005 22v. We just got it and have about 50 hours on it and generally run it basically non-stop for about 4-6 hours each time we are out.