LMM Fuel Economy

[RaiderCoach]

I purchased an LMM crew cab 4wd in May. The fuel economy was never better than 16 mpg hwy and 13 hwy city. I lifted the truck and put 33" tires on it and hoped that it was a break in issue. My previous truck, an 03 duramax, would average 15 mpg city and up to 22 mpg hwy empty and 14 - 17 mpg hwy towing, varied depending on weight of load from 7000 to 12,000 lbs. I had an edge juice programmer on that truck. I recently put a Bully Dog Power Pup on this truck, really hoping for some mpg results. Being able to correct the speedo was nice, the truck didn't really need that much more power. No matter what the setting that I have the Bully Dog set to, I am averaging right at 13 mpg in town and 17 hwy. I have a very light right foot, so unless milage would increase with a heavy foot, I am probably at about where I'm going to be. Currently the truck has 9400 miles on it. I really miss my 03 and wish I had stayed with it.

[craigth]

I lifted my truck with a ProComp 6" and 34" tires in Sept '07. You can see pictures in the TDP Photo Album page.

Interesting that you were able to adjust the speedo as the local GMC dealer said it couldn't be one with Allison transmissions! They also said that I couldn't have the tire pressure sensor set lower than 62PSI. However, a friend of mine with an '08 LMM 3500 said his dealership awas able to lower it in the 50PSI range. Not real happy with the knowledge and willingness to service non-standard features at the dealership.

Was the tuner worth it for performance? Did it make any noticable difference? Why did you select the Bully Dog tuner over another brand?

I wonder if GM knows about the LMM MPG issue?! I also wonder if this forum and the members of the TDP could use their numbers to communicate the issue and see if GM can tell us why and/or address the problem with some modifications.

It's really sad that in this time of high gas prices and diesel technology promoted as high mileage GM can't at least maintain or better yet increase the MPG of their LMM trucks. Most vehicles from year to year increase their MPG not decrease.

Maybe GM will get the wake up call they need when Toyota producesa 2500/3500 series of trucks with their own diesel! I'm sure their MPG will be high and more than likely the truck features and quality will be superior!

[RaiderCoach]

I went with the Bully Dog because the sales manager at the dealership that I use recommended it. My previous tuner, in my 03, was an Edge Juice. It worked really well, but I did have some stalling problems so I decided to try this one. The Bully Dog does allow you to tune the speedo to your tire size, although I have not checked it to make sure that it really did anything. There is definetely a power difference, although for street driving without a load, I don't really feel that there's a need for the increase. I netted about 1 mpg increase, far below the 3 mpg increase that I realized with my 03 and the Edge product. I would not recommend spending the $500 for that small of an increase. I'll be taking my truck in for it's 10k oil change soon and will talk to the service manager about the milage issue, although I know the answer already that I'll get. It will be "We're not aware of anything wrong"? Always the same answer, until GM sends out a bulletin in about 6 months...