I bought a 2022 Chevy 3500 6.6L Duramax Turbo Diesel and wanted to check the fuel economy for both towing and not towing. The numbers you'll see DO NOT include regen periods where the engine is burning excess diesel to convert soot in the DPF to ash. Also, the figures are from the truck's DIC (Digital Information Center) screen where the truck calculates the MPG via the trip gauge. Some people say those numbers aren't realistic and tend to be higher than actual. However, I checked those figures with eight stops at the pump (1400 miles in total), manually calculated the MPG and found there was good agreement between the two (within 1% on average). These were NOT fill-ups, rather, they were partials and averaged 14.5 gallons per refill.You'll see in the table the term "equation". This is the MPG using the trendline fit on the plots I generated. It's an arbitrary curve fit but does match the data pretty well. I'm simply comparing the curve fit with the averages for the speed increments I ran.I am pulling a 2018 Highland Ridge 5th wheel that is 32 feet long and weighs about 9000lbs loaded.Hope this is useful to some folks!https://ibb.co/BCWxTkp

Clickable LinkWere these tests done over the same route? In the same direction?

Mike in DE wrote:I bought a 2022 Chevy 3500 6.6L Duramax Turbo Diesel Dually or SRW?

My truck is an SRW, not a dually.The data was over different routes. However, I made sure the starting and stopping elevation was always within 20 feet. Also, trans temp was always between 136 and 144. Finally, wind was typically at a minimum. Despite those relatively constant variables, the variation in the data was still pretty large. That's why I kept getting more data points. I will add that I found no difference in MPG as the outside temp changed. In fact, there was a slight downward trend with outside temp when I plotted the numbers for 65 and 70 mph.

I'm going to assume mileage gets better with some age. I have a 3/4 ton Duramax with similar size but heavier 5th wheel. I average about 13 or better when towing and typically at about 70mph.

MPH vs MPG | Good Sam Community

StirCrazy
Moderator
Dec 31, 2022
Grit dog wrote:

It does lend some credibility to those who claim 25mpg out of their big diesels. But what they forget to mention is they’re drivin miss daisy and p!ssing off the line of cars behind them who may actually have some where to be before their next birthday.

you know, the older I get the less I car about thoes cars.. they can pass when its safe or use the left lane to go around.. especialy with fuel prices these days haha
Grit_dog
Navigator
Dec 30, 2022
Thanks for sharing. And not surprising. 50% fuel consumption increase giver take when towing a big sail has been the recipe forever. Nothing new.
Old Dmax and Cummins were in the 18/9 category around 70-75 mph (flat no wind). Newer Cummins is in the 14/7 range thanks to the lift, tires and too tall gears. Would be the same 18/9 if it was stock.
It does lend some credibility to those who claim 25mpg out of their big diesels. But what they forget to mention is they’re drivin miss daisy and p!ssing off the line of cars behind them who may actually have some where to be before their next birthday.
Thermoguy
Explorer II
Dec 30, 2022
I'm going to assume mileage gets better with some age. I have a 3/4 ton Duramax with similar size but heavier 5th wheel. I average about 13 or better when towing and typically at about 70mph.
Cummins12V98
Explorer III
Dec 30, 2022
Speed kills!!!
Mike_in_DE
Explorer
Dec 30, 2022
My truck is an SRW, not a dually.

The data was over different routes. However, I made sure the starting and stopping elevation was always within 20 feet. Also, trans temp was always between 136 and 144. Finally, wind was typically at a minimum. Despite those relatively constant variables, the variation in the data was still pretty large. That's why I kept getting more data points. I will add that I found no difference in MPG as the outside temp changed. In fact, there was a slight downward trend with outside temp when I plotted the numbers for 65 and 70 mph.
deltabravo
Nomad
Dec 30, 2022
Mike in DE wrote:
I bought a 2022 Chevy 3500 6.6L Duramax Turbo Diesel

Dually or SRW?
deltabravo
Nomad
Dec 30, 2022
Clickable Link

Were these tests done over the same route? In the same direction?

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