High octane fuel..
 

Anyone know if it really makes a difference if you pump say fuel rating 92 into a hummer. I have an h2 and when I put some in I felt it run smother and accelerated easier i don't know if it was just me or the fuel. Anyone else try it before? Is it worth it or just a complete waste of money.

Absolutely NO difference in mileage or power in my i5 h3. But I must say, every car responds a bit differently. I know if you get a tune designed for 93octane, it will help a lot between 93 octane and 87 octane.

The only thing I can tell you is try it. I've documented the mileage in my H3 very well, and upon testing with 93octane, it made zero difference. Now maybe joe schmoe's h3 down the road will like 93 more. So give it a try for 2-3 tank fulls. The highway is the bestway to test it since highway #'s tend to be more consistant.

Waste of money, it had no effect on my H2.

H2 here religious on tracking millage since I bought it and the higher octane didn't make even .1mpg difference. The only thing I thought I noticed was a slight change in the exhaust sound.

I personally think it is a complete waste of $.

The high compression '08+ 6.2 liter engines require high octane, according to the operator manual.

just fwiw
 

in my mustang days, my 10.5,460 liked Clark 93 the best. it wanted leaded!

The way mine sucks gas I couldn't afford to put premium in it.

Is there a hummer engineer that can comment on the hummer engines being high compression? I was under the impression they were not, I own a '03 for the record.

Compression Ratios / Octane
 

2008 HUMMER H2 - GM L92 engine
- 6,162 cc 6.2 liters V 8 all aluminum engine with 103.3 mm bore, 92.0 mm stroke,
10.5:1 compression ratio, overhead valve, variable valve timing/camshaft and two valves per cylinder
- Multi-point injection fuel system
- Power: 293 kW , 393 HP SAE @ 5,700 rpm; 415 ft lb , 563 Nm @ 4,300 rpm

The 2008 H2 operators manual says "Use premium unleaded gasoline with a posted octane rating of 91 or higher. You can also use regular unleaded gasoline rated at 87 octane or higher, but your vehicle acceleration could be slightly reduced, and you might notice a slight audible knocking noise."


2003 HUMMER H2 - GM LQ4 engine
- 5,967 cc 6.0 liters V8 cast-iron block engine with 101.6 mm bore, 92 mm stroke, 9.4:1 compression ratio, overhead valve and two valves per cylinder
- Multi-point injection fuel system
- Power: SAE and 235 kW , 316 HP @ 5,200 rpm; 360 ft lb , 486 Nm @ 4,000 rpm