LMM Fuel Economy

[Stlheadake]

Maybe winter blend fuel? I notice that in the cold I do get worse fuel mileage. Are you using a winterfront to keep the heat up as well. I notice an increase in mileage when I use my winterfront in cold weather. The truck seems to run about 20 degrees or more warmer. I get plenty of heat, but the performance seems to be better.

[MrBSA]

Hi Scott,
yes I wondered about the cold weather aspect. I don't use a "winter front" ( I assume you mean something that blocks off cold air to the radiator). Maybe I should try that. It has been a little cold here at times and the truck does take a long time to warm up. I do occcasionally add a fuel additive but haven't been able to determine if it makes any difference. I would like to try bio fuel but can't seem to find a station that sells it anywhere around here. Also having trouble finding a 15/40 synthetic motor oil other than "Royal Purple" which is a staggering 7+ dollars a litre. When our trucks take 9 1/2 litres that makes for an expensive oil change!!
Cheers,
Bruce

[RaiderCoach]

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!