What Grade of Gas To Use

[biffdotorg]

This thread is mixing the issues of 1) Ethanol and 2) Octane. Two completely different topics.

1. I've used ethanol in my 3 Yamaha boats since 2003 - never had an ethanol problem ever. I do put fuel stabilizer/treatment in over the winter that is specific to ethanol.
2. Octane is for high compression engines and prevents pre detonation (aka engine knock). If your engine doesn't call for high octane fuel you don't need it, and are wasting money buying it for a non high compression engine. It would be like lighting money on fire - total waste! The added octane in high octane fuels does NOTHING for a standard compression engine (non supercharged or turbo charged engine - many turbo charged engines don't need it either). Use the octane level the manufacturer recommends. Now, if you use lower octane gas on a supercharged engine, the engine will adapt and effectively lower the pressure on your engine to prevent pre-detonation (you will lose some power - 20-30% ish).

AMEN, I wish they would get rid of the word Premium etc, when it comes to octane. As it gives the uneducated the impression that its better for their engine.

 

[Julian]

In the owners manual it specifically states to use 91 or higher. Has anyone tried the non-ethanol in a jet boat and had any success or issues? Im under the impression the non-ethanol is better for the tank and hoses, but have never used it.

Lots of people have put ethanol free gas in boats. Some people, like Alexegan swear by it. Others like me could care less about ethanol free. Yes it will give you more power, but I'll take the savings on the gas over the power everyday. I've run this forum and the one before it and never seen anyone document a problem from using ethanol.

As for octane levels - don't waste money putting in higher octane gas than your engine needs. It is a TOTAL WASTE to do that.

If the spirit of the question was what is the “best” fuel option. Hands down that is 87 octane ethanol free for regular engines and 92 octane ethanol free for supercharged.

The question wasn't what the best fuel is. "Best" as defined how? Lowest price?
We'll simply have to disagree on your CHOICE on what "best" is defined as. For me, especially right now, price is a KEY factor. I'll continue my decades use of ethanol in my Yamaha with no ill effect and you'll enjoy your use of ethanol free for the "best" choice based on your criteria.

 

[ToddW850]

Sorry about this being an old post, but looking at my manual, it appears to call for either Minimum 86 Octane or 90.

"Recommended Fuel:
Regular unleaded gasoline with a minimum octane rating of 86
(Pump octane number) + (R + M)/2 90 (Research octane number)."

They heck does that mean?
@Julian being you and I have the same boat, what are you using?

 

[Thermobrett]

Sorry about this being an old post, but looking at my manual, it appears to call for either Minimum 86 Octane or 90.

"Recommended Fuel:
Regular unleaded gasoline with a minimum octane rating of 86
(Pump octane number) + (R + M)/2 90 (Research octane number)."

They heck does that mean?
@Julian being you and I have the same boat, what are you using?

I have heard mid grade pump gas is good for the non super charged engines. I use premium pump gas, but that’s because I have a supercharger. What the R+m/2 means beats me..

 

[Noko]

The (R+M)/2 you see on the label refers to the average of the research octane number (RON) and the motor octane number (MON) ratings. To determine the RON, the fuel is tested under engine idle conditions with a low air temperature and slow engine speed.

 

[FSH 210 Sport]

Sorry about this being an old post, but looking at my manual, it appears to call for either Minimum 86 Octane or 90.

"Recommended Fuel:
Regular unleaded gasoline with a minimum octane rating of 86
(Pump octane number) + (R + M)/2 90 (Research octane number)."

They heck does that mean?
@Julian being you and I have the same boat, what are you using?

You use a minimum of 86 octane that is on the big yellow button at the gas station. If you look at those buttons it will have R+M /2 formula on them.

RON is not used in the United States as far as I know.

 

[biffdotorg]

Sorry about this being an old post, but looking at my manual, it appears to call for either Minimum 86 Octane or 90.

"Recommended Fuel:
Regular unleaded gasoline with a minimum octane rating of 86
(Pump octane number) + (R + M)/2 90 (Research octane number)."

They heck does that mean?
@Julian being you and I have the same boat, what are you using?

as stated above, RON is not used in the US as much as Europe. 86 Pump octane is what you read on the pumps in the us.

Here, Let Me Google That For You

 

[ToddW850]

Awesome! Thanks for the explaination.