followup on Bio Fuel economy
OK, I ran two tanks of B50 (50% bio and 50% petro) in my LMM with the Bully Dog programmer set to the 'Towing / Economy' setting. Truck ran well, smelt horrible, and got worse economy than running at the stock settings with 100% petro fuel.
Even still, I'd like continue to run bio fuel...seems like the right thing to do. I don't know why the smell from the exhaust is so rancid though, on my previous '03 Duramax, it smelt like french fries or something, but on this truck with the advanced emission controls, it has a very acrid, harmful smell. Anybody have any insight to this? I'd hate to be running a fuel that's going to cause me to get cancer or something!
I did notice that speed has a very large part on the fuel economy on this truck. Unlike my '03, that seemed to get better mileage as you increased from 55 up to 75 mph, this truck goes the other way. At 55 mph I peaked with my trailer at about 13.5 mpg and at 65 I was at 8.5 mpg. Didn't even try 75 as I may not have had enough fuel capacity to make it to the next filling station:)!
Consistent average MPG is still 10-11 with 6K miles!
:( My average mileage is still 10-11 with 6K miles on my '08 2500HD Crew 4WD. A buddy of mine has an '08 3500 same model with 20K and other LMM work trucks. ALL get the same low MPG! Not sure how you guys are getting the mileage you claim!! How are you calculating your MPG?!
I'm very UNHAPPY with the mileage and am considering selling/trading for a Dodge Cummins. There is no way an '08 that is six years newer than my '02 should get 5 MPG less!
Another mileage update...
I now have 20K on my '07 LMM. My truck has 33" tires and a 4" lift, I'm sure that hurts mpg a bunch. I'm also running a Bullydog programmer at the medium (tow / econ) setting. Unloaded freeway driving I'm averaging 19 mpg and in town driving about 13. Loaded with trailer (about 12000 lbs plus truck), it drops down to under 14 on the hwy. I have found that the speedo correction from Bullydog does not work. I called them, but received the 'we haven't heard of that from anyone else so there's nothing were going to do about it' response. But, the speedo is off by about 3 mph, which would affect the mpg upward a bit, but I'm not a good enough mathametition (sp?) to figure it out. So the mileage is improving as the truck gets more miles on it. I would also agree that 55 - 60 is the sweet spot, at 70 I drop by about 2 mpg. Adversely, my '03 duramax improved it's mpg as the speed increased...