Real World Fuel Mileage

[LoneViper]

96 Dodge 5.9 12 valve 370,000 miles, constantly loaded with utility top and tools grossing 11,600#
353 gears and 5 speed. 68 MPH 17.2 - 18.0 75 MPH 15.3 - 16.2 towing at 68 14.0. Any time I can stay under 2000RPM I get 1- 2 mpg better.

Friend had a 1990 12 valve he consistantly got 21 -22 empty with 410 gears and 5 speed.

All milage is hand figured at the pump and is accurate.

 

[firecatguy]

I have a question.....how many of you go by the MPG that the computer displays? I see mileages stated at various speeds so are you just resetting the MPG display and seeing what it tells you at a steady speed??
Reason I ask is those things are quite inaccurate.....'03 6.0 Powerstroke computer says 17.5mph, but do the math and it was barely 13 combined hiway/city no towing.

i kept track on last trip out west going to do same next year also..something to do pass the time!!WATCH THE GAS GAGE GO DOWN LOLOL

 

[Bigs Apex Turbo]

If you have a duramax that is getting low mileage take it to a GM service shop and make sure they have a mechanic that knows about diesels and he can reflash the ecm and mileage should return to the high teens low twentys, I have an 01 duramax with 230,000 on it and doesn't miss a beat and still gets 20mpg on the highway at 70, and thats with a six inch lift and 35's.

 

[Osborne Performance]

have done that i had a o3 20 mpg edge programer was getting 18 loaded talk to are local shop i am a diesel tech so at times i think i know more than they do. but they told me they would have to install a older ecm to get the mpg out of it i ask them if i could remove the cat then the milage would go back up you know the answer to that. i am not complaing of the power i know hp and torque driven right in a light pickup geared for a low rpm means mpg

 

[Beels]

01 gmc 2500hd 4x4 crewcab short box,8.1 [496 big block] with allison auto. 3.73 rear end.6" lift 35" tires. 80 mph empty 12.5 mpg 65mph empty 15 mpg. 80 mph 24' loaded enclosed trailer 9mpg. 65mph with the same, 11mpg

I have the exact same truck except no lift & 265/75R16 tires and I get the exact same mileage as you quoted. The only place the 8.1 is bad is if you just use it for a grocery getter around town, and all trucks are somewhat bad in that scenario.

 

[CBX]

I agree with you on the new rigs...doesn't make sense to spend the extra $ (closer to $5k) on the diesel engine when they are getting worse mileage than the older ones. But, if you buy lightly used and let the original owner take the hit, it'll pencil out unless the price gap for fuel gets larger.

I'll take my '03 Cummins over my '08 F-350 gasser any day...much better mileage, more power, and just plain better for towing.

And to anyone claiming much over 20 mpg consistently out of a heavy truck, please share your secrets...maybe one of those Tornado devices stuck in the intake:rolleyes:

i get told constantly that i'm lying about my milage from my buddies. i drove to salmon, Id last week with one of my nay sayer buddies. went there and back (about 500 miles) and still had just a hair under a 1/3 of a tank left............i said to him "now do you belive me" he couldnt belive it. thats the guy with the 13mpg 6.4 ford.

on the D-maxes EGR block helps. one of the problems with that platform, at least the LB7,LBY,LLY (i've never been around an LMM) has is that the engine fan seems runs constantly. that sucks out a ton of energy. its takes a good 30-50hp to drive an engine fan.

far as the CR cummins goes, they really start working well once you get at least 50k miles on the truck. the rokktech crankshaft sensor is a really neat deal. its just machined so that you can adjust it from stock to 2 deg advance in .1 deg increments by using electrical tape pieces as shims. i run mine in the full advance. that does several things.

if you guys have noticed or remember how all these newer rigs run so much hotter EGT wise. thats due to the burn in the combustion chamber. EPA has placed emphasis on NOx reduction. so in a sense whats happend on these stock rigs is that they've been "detuned" from a combustion standpoint. well, the crank advance changes the burn in the chamber. it uses more energy form the combustion event to drive and force the piston down rather than just let the heat energy go out the exhaust. it also utilizes some of the fuel energy from the 3rd injection event that my 05' dodge has.

what makes it work so well is that torque from idle to around 12-1300 is noticeably increased. rokktech claims around 20%, and it sure feels like it driving it on the bottom of the rpm range. so what happens is you can drive with the first 1/2 inch of throttle and still keep up with traffic just fine in town. it also takes less throttle to maintain equal power compared to stock. down side is that warmup time is greatly increased in winter driving.

their muffler is really neat too. it cancels out all drone once your above 1500 rpm or so. its tuned in a way that it doesnt build back pressure either. no packing to wear out also.

how you drive is 90% of fuel economy. with my setup, i can drive like there's an egg under my foot, and still keep up with the pace of traffic. its a win win in my book.

i havent had a chance to tow very heavy with it since i put the sensor back in. since diesel is so dang expensive anymore, i'm planning on running it next winter and just live with the longer warmup time.