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3.0 Liter Duramax To Get An Upgrade

I used to hand calculate my fuel mileage on my LLY Duramax. I averaged around 24mpg on all highway runs and 18-19 for all other driving. I would have thought the 3.0 liter 6 would have done better.
My last hand calculated fuel mileage run was done last year. From RI to central PA. Doing around 78-80 mph on highway with 198k on the odometer I got 22.4 mpg. And that was with my turbo stuck with vanes wide open. I get about 18mpg around town here still. Not too shabby for a 6.6liter diesel V8.
But as I am getting older I am looking to my next vehicle purchase. Still up in the air. Just have to figure how much the belt change will cost, and how difficult it is.
 
RI Chevy Silveradoman said:
I used to hand calculate my fuel mileage on my LLY Duramax. I averaged around 24mpg on all highway runs and 18-19 for all other driving. I would have thought the 3.0 liter 6 would have done better.
My last hand calculated fuel mileage run was done last year. From RI to central PA. Doing around 78-80 mph on highway with 198k on the odometer I got 22.4 mpg. And that was with my turbo stuck with vanes wide open. I get about 18mpg around town here still. Not too shabby for a 6.6liter diesel V8.
But as I am getting older I am looking to my next vehicle purchase. Still up in the air. Just have to figure how much the belt change will cost, and how difficult it is.
Click to expand...

Wow, your fuel mileage is better on your truck than my Chevy 2500HD. The best I ever got on the highway was 22.8 MPG, that was some 55 mph to 65 mph driving flat ground, no mountains. Generally on the interstate running about 70 mph, I can get from 19 to 20 MPG all day long, that's about it. Local runs here in the mountains, seems like it's 15 to 17 MPG, if I remember correctly, hadn't checked it in a while. Your driving style might be different maybe? I very seldom do jack rabbit take offs, but I will blow the soot out of it ocassionally. Trying to figure the difference in our trucks. I assume yours is similar, I've lost track about yours. Its a GMC, crew cab 4x4, 3.73 rear gears, no camper shell? I've got the camper shell on my truck, empty, it weighs 7,340 pounds If I remember correctly. I've got 3.73 rear gears, 4x4, crew cab and as I mentioned before it's the LBZ motor, 360 HP, 650 ft/lbs of torque if I remember correctly. Maybe if yours is the LLY, it gets better fuel mileage?
 
I have the Chevrolet 2500 HD crew cab. Nothing on the bed. I upped tires and adjusted for size on my tuner. I was shocked that I had better fuel mileage at 75-80 mph than I did at 65-70.
I did use a sheel of plywood to make a Portuguese bed cover for the airflow and to cover my stuff in the bed. That may help lower air turbulence. Provide better air flow across the bed with plywood in place.
My best tank was 24.8 mpg going from RI to Loudon, NH for Nascar race. 4 guys in cab. Hand calculated with 90hp Hypertech tune. Much lower mileage on odometer and turbo was in full working order. Lol
I gotta get that turbo fixed.
 
RI Chevy Silveradoman said:
I have the Chevrolet 2500 HD crew cab. Nothing on the bed. I upped tires and adjusted for size on my tuner. I was shocked that I had better fuel mileage at 75-80 mph than I did at 65-70.
I did use a sheel of plywood to make a Portuguese bed cover for the airflow and to cover my stuff in the bed. That may help lower air turbulence. Provide better air flow across the bed with plywood in place.
My best tank was 24.8 mpg going from RI to Loudon, NH for Nascar race. 4 guys in cab. Hand calculated with 90hp Hypertech tune. Much lower mileage on odometer and turbo was in full working order. Lol
I gotta get that turbo fixed.
Click to expand...

Tuner might just be the difference? Also, for the life of me I dont know why you might have a GMC, after all, your screen or ID name on here has Silverado in it, I'm just not with it today.
 
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