Duramax vs Power Stroke Fuel Economy Tow Test and Drag Race

Cummins12V98 wrote:
"I think the 3.42 rear end on the GM might have had an effect on mpg here especially if they let the truck do all the shifting."

But But, I thought the magical 10 speed was supposed to keep the engine in the perfect rpm???

This is not due to it being a 10-speed but rather the trans tuning. Shifting manually or having a shorter final gear would alleviate this. To be fair, I had to do the same in my 68RFE when it had stock trans tuning and so do my friends and family who have Aisin's so Ram's stock trans tuning is not perfect either.

Cummins12V98 wrote:
"He ran just short of 60 miles (55 ) without towing and averaged 23.2 mpg."

I thought "incredible" driving my new 11 HO DRW for the first time with 13 miles looking at the instant and average mileage. Fact is I didn't see those numbers after a few hundred miles.

I do hope those numbers hold true but I doubt it.

I will be able to verify that shortly.... I am hoping for similar results but mine was ordered with 3.55 , the one reporting has the 3.31. Although I Can't see that huge of a difference

"I agree that the computer may be more accurate for short runs which this one was. If they had burned 20 gallons or more then I would be more inclined to believe the hand calculated number."

It's simply the stupid way they do the click wait click fill that can in no way be accurate. Maybe someone is filling on the pump next to it??? Then the pump pressure will be different.

Fill that sucker to the top each time! I do it every time, sure it takes a few more minutes but I know EXACTLY what amount of fuel I used.

That tiny DEF nozzle is very sensitive, no way that is accurate.

"IF I let the computer do the shifting allowing it to go into 6th. If I lockout 6th and to in 5th(which is still an overdrive gear) then that brings my rpms up to the Cummins recommended rpms of 1,800-"

Let's stick to reality. If "you" are pulling a steep grade letting the trans do it's job you are NEVER seeing 6th.

I towed with 3.42's at 29k combined and yes on FLAT ground it would go into 6th but you put a hill in front of it and 6th was a long lost memory.

The GM simply did not do what it should, electronics???

FishOnOne wrote:

4x4ord wrote:
The problem with doing mileage tests over a short distance like this is that if during the test the Duramax happened to do a DPF regeneration and the Ford didn't the results are meaningless. I think it takes roughly a gallon of fuel to clean the DPF so on a run where only a few gallons of diesel is required the mileage result could be way off.

I thought about that but if a truck did do a regen I think the mpg delta between these two trucks would have been greater. Plus towing this much weight there should have been passive regen working in their favor.

in colder weather my truck will go a long ways before the DPF is full but on average I'm going to guess it cleans about once every 500 miles. All it would take to screw up the test is for a regeneration to be triggered anytime in that short test loop. If the Duramax happened to start a regen even 5 miles before the end of the test, the test is flawed. To really do a proper comparison they would have to run both trucks an entire cycle; start with a clean filter and end with a clean filter. Then calculate miles per gallon based on the distance travelled even though it would be a different distance for each truck. Is it possible one truck regenerates 30% more often than the other or that one uses more fuel to do its burn? I might put quite a bit of emphasis on fuel economy when making a truck purchase if I felt the fuel economy tests were accurate.... as it is I think I would purchase the truck I wanted and if it happened to be the one that got the best fuel economy during the comparison, I would feel a little better about my choice.

"I think the 3.42 rear end on the GM might have had an effect on mpg here especially if they let the truck do all the shifting."

But But, I thought the magical 10 speed was supposed to keep the engine in the perfect rpm???

"He ran just short of 60 miles (55 ) without towing and averaged 23.2 mpg."

I thought "incredible" driving my new 11 HO DRW for the first time with 13 miles looking at the instant and average mileage. Fact is I didn't see those numbers after a few hundred miles.

I do hope those numbers hold true but I doubt it.

4x4ord wrote:
The problem with doing mileage tests over a short distance like this is that if during the test the Duramax happened to do a DPF regeneration and the Ford didn't the results are meaningless. I think it takes roughly a gallon of fuel to clean the DPF so on a run where only a few gallons of diesel is required the mileage result could be way off.

EXACTLY, but have you ever had hand calculated mileage on your Ford better than the computer showed? I'm talking filling to the top same pump.

ford truck guy wrote:

A member i know on this forum got his 2020 - 6.7 and just emailed me this..
He ran just short of 60 miles (55 ) without towing and averaged 23.2 mpg.

ROFLMAO, post of the week!

(And I'd call bullchit on the Ram Mafia or Bowtie wearin folks just the same for a claim like that.)

Not to disparage the claim, it could be totally accurate, under the right set of circumstances....downhill, believing the computer generated mileage (it may be right though), tailwind and hypermiling at the same time or drafting a slow moving semi all come to mind.

It does not speak for the "average" mileage for "normal" driving though. No magic potion under the hood of the Superdoody or any other truck for that fact.

4x4ord wrote:

"The problem with doing mileage tests over a short distance like this is that if during the test the Duramax happened to do a DPF regeneration and the Ford didn't the results are meaningless. I think it takes roughly a gallon of fuel to clean the DPF so on a run where only a few gallons of diesel is required the mileage result could be way off."


When the particulate filters fist came out it seemed that everyone doing a test would go to great lengths to trigger a regen before starting the test. I don't see that anymore are have wondered how that affects the test data.