New Chevy 6.0L gasser -- Octane?

[monkey44]

Just bought the new Chevy 2500HD with 6.0L gas ... and wondering what you guys run for octane.

And why you choose it? -- The 'why' is important too ... because it's not just about mpg, it's about engine performance and wear as well.

Doesn't bother me to buy higher octane as long as it benefits performance ... but am not sure if it makes a difference in the computer fuel management on these new 6.0L engines.

In the HD trucks - it does not offer the 'cylinder selection' option, so it always runs on all eight. The truck is 'labeled' a flex-fuel engine, but I don't really think that matters at this stage ... trucks have been flex-fuel for several years, without that label on the gas cap.

[Redsky]

Octane is a measure of anti-knock or pre-combustion that can occur before the spark plug is able to ignite the fuel and before the piston is in the correct position, hence the knock as the gas pushes back against the piston on the upward stroke. Higher compression engines are more prone to pre-combustion and need higher octane gas.

Gas engines in trucks are engineered to run on regular gas. Burning a higher octane rated gas accomplishes absolutely nothing with these engines. Using a higher octane rated gas than the manufacturer specifies is about as dumb a thing as anyone can do. It will waste your money and can do nothing for the engine's performance as the higher octane gas does not have a higher btu value.

Take a high compression engine that is designed for high octane gas and use low octane gas and the engine computer will retard the spark to compensate and power will be lost and usually the fuel economy will suffer as well. But that is entirely different from using a higher than needed octane rated gasoline in an engine.

Better to put your money where it will affect the performance and longevity of the engine with regular maintenance and the occasional use of a fuel injector cleaner.

All engines will knock to a degree when under a heavy load at full throttle as when going up a steep grade and that is not indicative of the gas having too low an octane rating.

[APT]

87 is all that is required and will not get higher performance or use less fuel for higher octane alone. But E10/E15 is very common across the USA. Some stations do not use E10/E15 for higher octane fuels, which does tend to decrease fuel consumption.

GM does recommend using TTG.

[monkey44]

McDonoughDawg wrote:
What does the owners manual say?

I am guessing 87.

If so, that is what I would run.

It doesn't specify - it says it will run on all three, and 85 ethanol will run in this truck. It doesn't tell me which is best.

I'd prefer better gas mileage if I have the choice, but not at the expense of the engine running or wearing or costing more repairs later ...

I'm fine with the 87, have been running it for years in my 2003 6.0L, but was wondering if there is some greater benefit in the new engines if we run higher octane. Apparently, there is not anything specific enough to change.


With the newest electronics, I just wasn't sure - and am not a mechanic, so thought some guys on here would know better than me if one is better for some specific mechanical or electronic reason.

We haul a truck camper, not a heavy trailer. It's about 3200 lbs. and I get the 2500HD because of the weight on the axles not because of towing a heavy trailer. This one has a 4:10, although I'd have preferred the 3:73 like my last truck - which hauled this camper just fine ...

[McDonoughDawg]

What does the owners manual say?

I am guessing 87.

If so, that is what I would run.

[cruise-ader]

I run 87 on my 2008
I have tried 93.
My "butt dyno" or non scientific mpg formula gave me any indication or added value or mpg increase.
Might get a tad more power when pulling, but that's not enough for me to justify the $.30 more /gallon.
If it got me 2-3 mpg more, I would. But it doesn't. Unless my trip is downhill both ways.

[Turtle_n_Peeps]

monkey44 wrote:
Yeah -- I wouldn't run the 85 ethanol either ... we have 87-89-91 here, and the dealer actually got back to me today and says the engine is set up for 87 from the factory. So, I'll try it for a few tanks each and see what happens.

I was just wondering what other trucks run and why it might be better one or the other. Don't care as much about the savings per gallon as I do the best performance of the truck - I plan on owning this one for a long time and want to treat it right from day one ... our truck will take care of us if we take care of it ... That's my thought anyway.

Depends on what you want?

You say "Don't care as much about the savings per gallon as I do the best performance of the truck."
What kind of performance? Most HP? If so, fill her up with E85 and hammer down. That is where you will find the most HP.

Most MPG? It's going to be VERY close between regular and premium if both have Eth in them like we have out in Ca. You will get right at 4 to 5% better fuel economy with no Eth. Like I said above, it can even boil down to weather or even altitude for octane. So if fuel economy is important then get one with no Eth.

Bottom line is:

You want power? Get a fuel with the highest alkie content possible.

You want mileage? Get a fuel with the lowest alkie content possible.

Wear? Really no difference between the two. The OLM will more than likely go off sooner if you use E85.

[MFL]

APT wrote:
The only reason to use higher than 87 octane with the stock GM 6.0L is if it meant no ethanol vs. E10/E15.

I agree, and also the reason I filled 91 on last two fill ups.

re: my earlier post

My choices were 85 regular, 87 ethanol, or 91 no ethanol.

Jerry

[APT]

The only reason to use higher than 87 octane with the stock GM 6.0L is if it meant no ethanol vs. E10/E15.

[fla-gypsy]

I would use whatever the owners manual recommends. Non ethanol will always deliver better mpg's.

[monkey44]

Yeah -- I wouldn't run the 85 ethanol either ... we have 87-89-91 here, and the dealer actually got back to me today and says the engine is set up for 87 from the factory. So, I'll try it for a few tanks each and see what happens.

I was just wondering what other trucks run and why it might be better one or the other. Don't care as much about the savings per gallon as I do the best performance of the truck - I plan on owning this one for a long time and want to treat it right from day one ... our truck will take care of us if we take care of it ... That's my thought anyway.

[dwb619]

The gm badged "Flex Fuel" means that the engine will operate on E85.
Be prepared for about a 30% decrease in mileage if you burn the E85 alcohol.
On another note, I just noticed my 2014 5.3 makes 355 hp on gas and 380 hp on E85.
383 pounds torque on gas and 416 pounds on E85.
Haven't tried E85 and have no plans to.

[TomG2]

Biggest improvement with the GM 6.0 that I have found has been when I run ethanol-free. It improves fuel mileage 10-12%. I have trouble finding it these days.

[RAS43]

DavisK wrote:
This makes me wonder about a lot of comments I've read in other places. I read that others buy gassers instead of diesels because the fuel is cheaper even though the diesels get better mileage. Today's fuel prices where I buy: Premium - $3.50, Diesel - $3.54.

You are fortunate. Right now around here diesel is 40cents more then gas and has been higher. Makes one think more about the diesel/gas decision as far as fuel costs are concerned.

[spoon059]

I think they run fine on 87 octane. If I remember correctly, that is what GMC recommends. That being said, if you can by 91 octane that is ethanol free, you will probably get better mileage simply because it doesn't have to make popcorn too...

[Taco]

I run 87 in mine, works fine for me.

As far as the diesel to gas spread. It has tightened up around here to about 40 cents cheaper for gas it is almost always 60-70 cents more for diesel but I have seen as high as a 90 cent spread.

I don't know where in VA that other guy is but I can get unleaded 87 around here for 3.20