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

[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.