[Mariah Z276]

$3.37 a gal. for regular, and now you say I should move up a grade because of ethanol. It already takes $400.00 to fill up.

[KSP181]

I'm sure that I am not the smartest person on this board. With that said...My understanding is that octane is the resistance for predetonation. The higher the compression of your engine the higher octane you need to prevent predetonation. If your engine does not need a high octane to prevent predetonation (87) and you put high octane in it, then you will see no advantage.

People sometime confuse high octane with high performance. If your engine is built with high compression then high octane is needed and you will see a loss when using low octane fuel (predetonation). If your engine is build for low octane (low compression) you will see no improvement when useing high octane.

There are several websites that discuss octane ratings if you need to find out what fuel to run to get the most out of your boat without wasting money.

[WetWilly]

Hi KSP181

I don’t think anyone here can claim their the smartest, that’s for sure… that said, you’re absolutely correct about the pre-detonation and if anyone is interested in learning more about Octane they can click here: octane rating.

There is one situation where higher octane can improve your performance - at times when the engine is under extreme loads such as a boat very heavily loaded with people and gear and expected to run flat out. The higher octane would suppress pre-ignition allowing a higher top speed because the operator would not have to back the RPMs off as soon due to engine pinging. This is the same for a tow vehicle when pulling a grade

There’s a little know secret - there are vehicles designed to run on 87 octane, but when higher octane is used, the computer recalibrates the fuel injector duty cycles and engine timing to take advantage of the higher octane (or lack of ping). One such example is the Ford Triton series. Though the gains are small (I have heard up to 6%), it can make a difference while towing and acceleration. I have tried it out myself after hearing of this back in 97 and later on our 99 with a re-programmer for the engine computer.

Hey Mariah Z276, if the octane you’re using does not ping when you’re out and about, then you’re OK, but if you’ve got the knock, it’s up the grade of gas or look at getting another motor some time in the near furture. What’s an extra $5 to $10 bucks compared to another motor, right?

Believe me when I say I totally sympathize with everyone with larger V8 motors. For the last 24 years, I ran a 3.0L and now I have a 7.4L. So you can imagine what I'm having to get used to at the gas pump. What makes it worse is, many stations here limit the dollar amount per fill up to $50.00. That won't even fill the Expedition's tank let alone put a dent in the Talari's...OUCH, but I figure that's the price I have to pay for that extra gettiyup and go!

Sorry, just my $0.02, make that $0.04 worth of ranting,
WetWilly

[moondance100]

$3.37 for regular? What a bargain! Everyplace I'm seeing is $3.60-$3.65!!! I only burn about 5-10 gallons per week. If someone wants to ski or kneeboard, they better bring a $50 bill with them!

[Mariah Z276]

Thats good news. I don't have any pinging. It was mentioned earlier in the thread that with ethanol you need to up the octane. Thanks to you and KSP181 for the explanation.

[Z 202]

Around here most gas stations dump all the ethanol in during the winter, which kills your winter mileage. So it's less likely to be an issue during the boating season.

As stated in the Mercruiser link WetWilly provided, the merc design should handle 87 octane with up to 10% ethanol, and as noted, the only reason to go higer is if you are experiencing detonation when under load.

[180diablo]

There is a lot of good information about fuel in this thread!

I think im going to give my 3.0 a hug when I get up to the cottage.
lol.

[WetWilly]

Originally Posted by 180diablo

There is a lot of good information about fuel in this thread!

I think im going to give my 3.0 a hug when I get up to the cottage.
lol.

Uh, I think there may be a law against getting intimate with your sterndrive....

[180diablo]

Ummm no .. only in Alabama there is

[Z275]

As I've said before the most important thing is to stay away from gas with Ethanol in it! At most marinas this won't be a problem but a lot of us fill up at gas stations before getting to the water. This is where you have to be careful. Most mix 10% ethanol with their gas now.