2008/2009 owners..... Premium fuel question??

[MVR 155]

I had to tow a pretty good sized trailer this weekend..... 32' Sunsation Dominator offshore boat with 2 496 H.O. engines, 110 gallons of fuel and a very beefy tripple axle trailer along with gear (clothes, coolers etc....) We estimated the total trailer weight to be close to 9,000 lbs. Its been pretty hot here (around 90 degrees) so I decided with towing that load in the heat I would fill up with 93 octane vs. 87 octane I usually use.

First let me say how impressed I was with how this drivetrain tows, pulled it very well, I was expecting the truck to be laboring bad with that kind of weight behind it and was litterally shocked at how good it pulled. Tow/Haul mode works fantastic.... My friend has a 2005 3/4 ton Duramax with a Banks System installed and he couldnt believe how good the H2 pulled the trailer (he had a rear caliper go south the evening before we were headed out.....good thing it happened before and not while we were towing).

Since I filled up with the 93 octane 1 block from where I picked up the trailer I didnt really get a chance to drive the truck "unloaded" prior. After dropping the trailer off late last night I couldnt believe how much better the truck drives with premium fuel..... it is way more responsive in the 2,000-3500 RPM range, It really feels like the computer is pulling some timing while running the 87 octane fuel as I feel I need to lean into the throttle in the lower RPM's more. It also seemed to shift better at low speed, I sometimes get a thud when I slow for a turn and get back on the gas (like the trans is hunting for a gear).... Didnt notice this once on the way back.

Anyone else see tell tale results running the better fuel?

[splne1]

Yep I agree!! On my many trips back home to Texas I can definently tell the difference when premium is in the tank. I have towed some sand toys around back home and yes the difference is noticeable.

[pat123]

I have only had my H2 for about three months but I only use 93 octane fuel (I just got used to it with the 2007 Vette that I traded for the Hummer) so I do not know how well or poorly it runs on lower octane. I only drive mine on the weekends so paying for premium fuel is not that big a deal to me.

[MVR 155]

Splne 1..... with being on the road do you notice any improvement in gas mileage running the higher octane? Im sure any gain is offset by the higher price of the fuel but I was simply curious. Thanks

[dvl57]

I've filled my 08 w/regular 89 octane and had no issues.

I've tried using premium 93 octane...but I didn't notice any difference.

Then again, I never towed anything.


My Hummer dealer in Houston said it runs the same...w/regular as premium.

Who knows?! It could be preference or opinions...but I always tend to use regular.

[splne1]

Originally Posted by MVR 155

Splne 1..... with being on the road do you notice any improvement in gas mileage running the higher octane? Im sure any gain is offset by the higher price of the fuel but I was simply curious. Thanks

On cruise control it gains maybe 2 MPG's but nothing really to Jump about. But remember I am running it lifted on these big 37's. I also have a Hypertech programmer installed with the K&N intake. Im sure if it was stock height I could possibly get better MPG's.

[VegasGuy]

Don't underestimate the placebo effect.

[MVR 155]

Vegas....... Im well aware of the Placebo effect, have owned alot of modded cars/bikes and dont usually count horsepower till I see it on a dyno or get results at the track. I too laugh at posts on forums about the guy who installs a K/N filter and can feel a "HUGE" boost in horsepower....

Im not talking a night/day difference but there is a noticeably better response in the lower RPM along with the trans acting better.

I owned an 06 prior to this 08 and running premium did nothing in that truck so I can see how you may make the "placebo" statement based on the fact that you own a 2005..... there have been past threads here regarding the use of premium in the 2008/2009's due to knock issues, rough idle, low RPM gear hunting and clunking etc....

[seventwozero]

FWIW, When I bought my 04' the salesman told me because of the 6.0 a 'top tier fuel' should be used, nothing cheap! I've personally never tried it albeit I have a 800 mi road trip in a couple weeks, I'll give some premo fuel from Minneapolis a shot on my run home and see if it makes a difference. Top Tier stations are few and far between up here in the Dakotas, cheapo Tesoro and BP

[jmanley]

I just got back last night (4am) from a 2800 mile trip from ND to MT to ID to WY and back again - varying terrain from flat land to mountain passes.

Didn't really seem to matter if I had 87 / 88 / 91 / 92 octane in it, it ran about the same, though on the days I knew I was either offroading and/or going over a pass, I tried to keep higher octane in it merely for a safety factor.

I will say, though, watch your tranny temps! I was pulling a trailer on some days (probably 1.5 ton total weight) over the passes, and even though air temps were as low as 58F, my tranny was hitting 238F !!!!!!

I have the stuff to do the conversion to an external cooler, just ran out of time. BTW - I'm going to write it up as I have figured out a way to do this w/o cutting lines.