What octane fuel is everyone running?

[MLA]

I don't mind paying for the better fuel,

Octane is not a quality indicator. Its a measure of its resistance to self ignite.

Most all newer high compression engines are going to the cooler burning octanes.

You're close. Once ignited, 87 and 93 have about the the same BTU's p/oz. The difference is that the 87 will ignite at a lower point then the 93. Higher compression engines have a higher combustion temp, so the we need a higher octane in order to resist pre-ignition.

Ethanol blended has a lower BTU and MPG then pure gas of the same octane. Thats why many notice a difference in fuel mileage between pure and E-10 gas.

[wario]

I’ve been told by two separate dealers selling indmar powered products that 87 is fine to run in the 400.

[larry_arizona]

I’ve been told by two separate dealers selling indmar powered products that 87 is fine to run in the 400.

As long as the ECM has high and low octane timing tables and utilizes Knock sensors to put it into the low octane timing table, I would agree.

Lower timing means reduced power but would be safe if 87 was all that was available.


E85 is badass in forced induction applications, it’s typically 100-105 octane. It’s truly race gas.

I have a 2010 CTSV with an LSA 6.2, E85 is amazing in supercharged engines.

But you need enough fuel pump to run it, flex fuel sensors and hybrid tuning for gas and E85 simply because E85 availability is still so limited. E50 seems to be the biggest bang for the buck (mix of 93 and E85 until flex sensor reads E50ish)

All said thought, E85 would suck for boats as it would draw so much moisture.





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[Broke Pilot]

All 89 gas is just a 50/50 87-93 mix done at the pump.
Worst case scenario just throw half 91 or 93 in there until you can get 89

[mikepo26]

i run 87 in my 08 lsv, everything newerish has a knock sensor so whatever you run it will retard timing if knock is detected

[Darter]

We use 89 as that's the lowest octane we can get without ethanol. Our local 87 has 10% ethanol.


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[AtTheRiver]

I run E10 87 octane all summer and will put the blue Stabil for ethanol every second or third time I top off gas. I rarely let it go below 1/2 tank. When the boating season is winding down, I will run whatever octane ethanol free gas I can get. Finding any ethanol free is a small challenge and some stations only carry 87 others 93.

The longer your ethanol based fuel sits around the more likely you will get phase separation and H20 in the gas so do not worry about it when I am filling the gas up every week or 2.

[DatTexasBoy]

93 all day.

[Kidder522]

I run 91 all the time.


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