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]

APT wrote:
Redsky, I generally agree that higher octane alone is a waste. But many drivers experience lower fuel consumption by using 100% gasoline vs. E10/E15.

Ethanol mixes are very different and they do damage engines in much the same way as biofuels can seriously damage diesel engines. There is also the matter of the model year. Just as some gas engines are pre "flex fuel" and more readily damaged by ethanol mixes, so too are pre-2010 engines more likely to have operating problems with biodiesel and B20 especially.

The ethanol mix was increasing as people have been driving less and using more fuel efficient vehicles but the corn lobby got the laws written to force the gas industry to buy a fixed quantity of ethanol regardless so the percentage used has increased steadily. Congress was supposed to change the law but then we now have the do nothing House that has done less than any Congress in the past 200 years so who knows.

[ksss]

TomG2 wrote:
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.

I found that to be true as well. There is a gas station here that gets ethanol free gas at the lower octane ratings for the same price as 10% ethanol gas.

[brholt]

intheburbs wrote:

brholt wrote:

Redsky wrote:

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.

This doesn't seem to be the case for the Ford 6.2L:

Quote (taken from Ford Truck forums when the 6.2 was introduced in 2010. Mike is a engine engineer

"Originally Posted by Power Kid
Mike, I just read that the 6.2L in the Raptor has 411 hp on 91 and drops slightly to 401 on 87. Is there a drop off on the SD version as well? Or is it 385 straight across?

The Superduty version is SAE rated on 87 octane (R+M/2) so it is directly comparable to the 401 hp for the raptor. You will pick up power on the 6.2L Superduty with 91 (R+M/2).

Mike."

Link

Your conclusion is backwards. The standard engine won't "pick up" horsepower by running 91 octane, the Raptor engine is derated slightly when the computer senses the lower octane.

My Chrysler 300 with the Hemi does the same thing. 89 octane is recommended, but the engine will run slightly derated on 87 octane. The lower octane gas is more likely to detonate in the higher-compression engines, so the computer adjusts the timing, reducing engine power.

Engines designed for 87 octane don't sense the higher octane and increase power. That's what aftermarket PCM tunes are for. I had my 2001 Suburban tuned for 91 octane, and the tuner used more aggressive timing. His tests showed an increase of 15-20 hp on the 5.3L.

Not sure why you are saying it is backward. The Ford engine engineer was specific that the 6.2L in the superduties will change the timing and make more horsepower with the higher octane. There is more discussion in the tread if you want to follow it.

[Gale_Hawkins]

Again for little net cost run three back to back tanks of premium gas measuring the results any way you wish for the answer for any vehicle.

The old 1992 454 TBI in the MH makes more power on 91 vs 87 that the manual states to use. One plus for using premium grade in a dirty fuel system and engine deposits is the greater concentration of detergents can enhance performance.

[intheburbs]

brholt wrote:

Redsky wrote:

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.

This doesn't seem to be the case for the Ford 6.2L:

Quote (taken from Ford Truck forums when the 6.2 was introduced in 2010. Mike is a engine engineer

"Originally Posted by Power Kid
Mike, I just read that the 6.2L in the Raptor has 411 hp on 91 and drops slightly to 401 on 87. Is there a drop off on the SD version as well? Or is it 385 straight across?

The Superduty version is SAE rated on 87 octane (R+M/2) so it is directly comparable to the 401 hp for the raptor. You will pick up power on the 6.2L Superduty with 91 (R+M/2).

Mike."

Link

Your conclusion is backwards. The standard engine won't "pick up" horsepower by running 91 octane, the Raptor engine is derated slightly when the computer senses the lower octane.

My Chrysler 300 with the Hemi does the same thing. 89 octane is recommended, but the engine will run slightly derated on 87 octane. The lower octane gas is more likely to detonate in the higher-compression engines, so the computer adjusts the timing, reducing engine power.

Engines designed for 87 octane don't sense the higher octane and increase power. That's what aftermarket PCM tunes are for. I had my 2001 Suburban tuned for 91 octane, and the tuner used more aggressive timing. His tests showed an increase of 15-20 hp on the 5.3L.

[brholt]

Redsky wrote:

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.

This doesn't seem to be the case for the Ford 6.2L:

Quote (taken from Ford Truck forums when the 6.2 was introduced in 2010. Mike is a engine engineer

"Originally Posted by Power Kid
Mike, I just read that the 6.2L in the Raptor has 411 hp on 91 and drops slightly to 401 on 87. Is there a drop off on the SD version as well? Or is it 385 straight across?

The Superduty version is SAE rated on 87 octane (R+M/2) so it is directly comparable to the 401 hp for the raptor. You will pick up power on the 6.2L Superduty with 91 (R+M/2).

Mike."

Link

[Turtle_n_Peeps]

APT wrote:
Turtle, ethanol has lower energy content than gasoline but higher octane. I have read similar reports on random threads from several brands and types of vehicles, same octane of gasoline vs. E10 is about 10% difference in fuel consumption.

So if gasoline has 10% alkie in the mix and one gets 10% less mileage ergo there is no energy content in alkie? :h

See the problem here? :S

[APT]

Turtle, ethanol has lower energy content than gasoline but higher octane. I have read similar reports on random threads from several brands and types of vehicles, same octane of gasoline vs. E10 is about 10% difference in fuel consumption.

[Turtle_n_Peeps]

GeoBoy wrote:
When I am towing my TT I noticed that my 6.0 runs better on 89 octane. If I am just running empty I use 87 octane. When traveling with my TT, if I can find pure gasoline I noticed a 10% increase in fuel mileage.

Why would gasoline with 10% alkie in it get 10% less mileage? That makes no sense? :h

[intheburbs]

Redsky wrote:
Burning a higher octane rated gas accomplishes absolutely nothing with these engines.

This.

/thread

[GeoBoy]

When I am towing my TT I noticed that my 6.0 runs better on 89 octane. If I am just running empty I use 87 octane. When traveling with my TT, if I can find pure gasoline I noticed a 10% increase in fuel mileage.

[Supreme_Oppress]

Gasoline has more oomph than etanol. E85 gets lower mileage but is cheaper. For the most part, use what manufacturer suggest. It does vary though. I had a small tank and a 45 min commute so it was easy to test. tried 87, 91, speed limit, over somewhat - nothing made a difference so i used 87 octane at slightly above limit. When I replaced that car with a small truck (S10 with a 4cyl), mileage was about the same but performance difference was significant so I used 91.

My current car requires 91 minimum so its a no brainer. A co-worker has a truck that required 91 but he used 87 - right up until he needed the heads replaced because of extreme carbon build up on the valves.

[APT]

Redsky, I generally agree that higher octane alone is a waste. But many drivers experience lower fuel consumption by using 100% gasoline vs. E10/E15.

[monkey44]

Excellent -- thanks for all the advice / answers ... I kinda figured 87 was OK, but want to make sure I don't make a dumb mistake.

And, yes - regular maintenance and oil changes and all that - very good method to keep your truck happy. Happy truck equals happy campers.