I have a 2007 Chevy duramax CC with 275-75-18, stock with EFI live speedo changed. I travel about 15 mile one way average speed is 55-60 mph and fuel mileage is about 13-14 mpg. Does any else have this problem or is this normal?

I have a 2007 Chevy duramax CC with 275-75-18, stock with EFI live speedo changed. I travel about 15 mile one way average speed is 55-60 mph and fuel mileage is about 13-14 mpg. Does any else have this problem or is this normal?


I noticed in ambient temperatures below 50 degrees F, traveling short distances (less than 30 miles), my mileage is around 15 mpg on the freeway. After my engine temp. reaches 180+ degrees F, my fuel mileage goes up. What are the air temps and your engine temps when you reach your destination?

Out side temps are about 35-40 degrees and my trucks temp goes to 210 and right back to 191 and stays there. I even have the winter cover on. My old lly never got that bad of mileage. It always reached operating temps and stayed there.

Try a 300 mile run...Hand calculate, then, do another 300 mile run after about 35,000 miles.! You will see a difference. It is a common occurence for LBZ owners to see lousy mpg initially and for some it will last a while till the truck is truly broken in.

Tow with it, work it and the mileage will improve - sooner.

Most after a decent break-in will avg 18.5 mpg with an MT Truck - no wind - at 65-70mph. Lots of posts here on mileage and who gets what with what.

hang in there.

cheers
Stk

I noticed while I was in warmer states such as FL, SC the fuel mileage was better, the more north I went the worse it got. In my truck it is lousy in freezing temps compared to 60 degree and up temps and I have 35k on it.

Ryan..you want your old LLY back......LOL

Just curious if people that complain of lower mpg are allowing the trucks to warm up before driving?

no I plug it in my garage. Jump in and drive.

Was just wondering, I know if I remote start my truck and let it warm up some, usually takes my mpg 1-2 or more depending on how many mornings and afternoons I use it.

I think these trucks really suck the fuel on cold starts, maybe even worse than gassers to an extent. I noticed when taking my truck out for neighborhood spins I can go through almost half a tank over a 5 day period yet when I commuted in my truck to work (30 mi one way) for two days it's only drawn the tank down 1/4.

neighborhood = 30-40mph
to work = 50-65 mph

might that be the difference.?

Agreed that fuel consumption is somewhat higher in colder climes...where I live it has been below freezing pretty much since end of Nov. and will stay that way till mid March.

Still only have had to plug in for a one week spell, -25 to -35C in the evenings. Other than that, I let the glow plugs glow, start it up and go. I drive slow the first cpl of miles (low rpm), and then away we go. Still getting on avg 14 - 15 in the city and 18.5 -20 on hwy, speed depending. Usually MT truck with just the tool box loaded.

stk

I have a 07 with about 9000 miles on it. Run Hypertech111 on 2. Besides my long distance prospecting trips, my truck sits except for Saturdays (local prospecting trips) which average 70-80 miles round trip. Live in the hills, up and down and curves. On the DIC, I was averaging 14.5-15. On my second change of engine oil (at 8000m), I went with Mobil1 5-40. In the last 4 fill-ups DIC says I'm averaging 16.5-17.
I know motors not even close to being broken in and I'm not complaining; just did'nt think a synthetic would make that much of a difference.
Love my truck!
Shep

Mine was about the same, I got the superchips 2805, set on tow performane I get 20+ @60 mph, 16+@ 80mph, avg during the winter with warm up time 5-10 minutes on high idle is 14.5-15.7 mpg , these are numbers from the DIC, I hand calculated them and on the tow performance setting the DIC is only .175 gallons off of 18-20 gallons used. Close enough for me, by the way I'am no light foot .


1/8 mile time 10.02 74 mph