How much fuel mileage does one sacrifice going with the new 6.7?

 

I lost about 2 mpg from my old 12 valve with the mods.

 

My past truck was a 2004.5 quad cab. Essentially the same frame truck with the same size topper as I am driving now. Comparing fuel used for these two trucks at the same mileage over 10,000 miles. The 2004.5 averaged 17.63 mpg and the 2007.5 averaged 14.45 mpg. For me this works out to approx. $1000.00 per year .
Those of us driving clean air vehicles are paying a stiff penalty that those driving dirty air vehicles do not pay. It appears the oil company's are the main benefactors of our sacrifice.

 

Between my 2001 2500 6spd manual and now my 3500 SRW 6spd manual I have lost about 15 per cent towing or not towing due to the BS on this truck.

 

I can't compare since this 6.7 is my first diesel. But, I'm getting 12 or 13 city/highway not towing. And, 9 or 10 when towing about 10K. I'm pretty disappointed in the mpg. The truck and towing are great, but I don't think its that much better for the lousy mpg... Diesel is much higher $ than gas too right now (way higher than premium). The only way this thing pays off, is if you HAVE to tow something that others really couldn't do... Simple capability. With no power on reserve like this 6.7, my 5.3 gas suburban can tow just as fast 65 mph) with the same mpg and on way cheaper gas...

 

This helps with your other post. Even if you have 4.10 gears, I'd be documenting a complaint with the dealer. I don't care if it's brand new and tight, it should get better fuel economy.

 

Thanks, I responded to the other post. 3.73 gears. It seemsed like it was leaking diesel the way the gauge was moving... I could get 300 miles out of my Sub towing the same set-up. It's tank is 32 gallons.

I guess I'm paying a bit of a premium for the "power on tap" now. Even with the bad mileage it is better insurance than potentially killing my gas vehicle drivetrain... I'm just glad I don't tow that often.

 

I'm not an engineer, but I wonder what fuel consumption a redesigned 5.9 (insead of 6.7) displacement would have been?

If either redesigned motor gives you a 2 mpg loss with the DPF okay, but if not the bump in horsepower and torque seems to me an expensive loss for such a marginal increase. There is a lot of marketing ego in bringing more power to market to beat the next guy while sacrificing fuel economy IMO.

I've never had any problems whatsoever towing with the 5.9, anywhere.

 

I agree with what you're saying to an extent. It still takes X amount of fuel to generate the Y amount of hp needed to accelerate the vehicle to a Z velocity.

Even if you subtract some from Y (lower the max hp), it's still going to take X amount of fuel to generate the required hp to move the vehicle.

There have been changes to the 6.7L that increase the engine's mechanical efficiency (vgt and higher pressure fuel system), which theoretically would increase fuel economy. Cleansing the aftertreatment system is where the hit comes from.

 

Your mileage will improve for sure. My 05 opened up at about 12k, and then again at 50k. Following the speed limit, coasting to all red light (instead of using the brakes), and accelerating as lightly as the situation will allow has gotten me from about 16.5 to 18 on the first bump and then to 20ish recently.

I also check my tire pressures and run them as close to max as my lower back will allow.

Also keep watching this site for fuel economy improvements. customer's demand, aftermarket supplies.

One last thing is that I have seen a lot of comments about the lates PCM reflash somehow yielding better FE, so you may want to have your dealer make sure you have the latest PCM flash (and TCU for that matter).

 

Thanks Bigblock. I see your point. Makes sense.

In the future if they raise the 6.7's HP and Torque (idea behind more displacement?), still fuel economy should get worse unless they lighten the platform. I guess I'm saying at this performance level, I don't need more performance but better fuel economy and durability.

I don't want it to go faster, I want it to go further and last longer.

 

Thanks for those tips. I've heard that about the 5.9 and can only hope that the same "incremental" improvement may come for the 6.7. I understand that more cubes and more power with take away from FE, I just hope it can improve from here. I'm hoping for someone to tap into the 6.7's potential for improved economy. Reading other's posts it seems that people would sacrifice some of the awesome power for some economy and longevity... I'm sure someone will pump it up even further on power for sure.

 

No prob. I agree with both of you. I'd like to sacrifice some top end hp for increased low end torque and better FE.

We may see that in the future, now that the hp wars are switching to fe wars in cars with fuel prices and energy conservation taking the forefront.

 

I just had that done, and have seen about 1-1.5 mpg gain. I am now at 14.8mpg hwy, and 9mpg towing 14K

 

I have noticed a trend in the newer trucks started with a 99 quad cab hiway after break in was getting around 22 mpg. Moved up to a 03 crew cab after break in i was averaging around 20 mpg. Had to step up to a 05 crew cab dually. (bigger toy's) after break in around 18 mpg. Now into the 6.7 mega cab not broke in yet but early milage is showing a decrease 3rd tank of fuel only getting 14.2 unloaded hiway. I'm sure after a summer of towing the toyhauler and 3 harley's it will increase a couple miles per gallon but not expecting much. the one thing i will say is none of my trucks have ever left me stranded on the side of the road. I have pulled mutiple campers for other people with other vehicle makes because they have had to leave their truck at a dealership out of town for a fix. I'll take the milage hit as long as my truck gets me home.