Fuel economy changing

[ramphil09]

I have a 2014 2500 with 90,000 miles. Driving the same route (45 miles) everyday I have noticed that some days the diesel economy may read 21 to 22mpg and other days 18-19mpg and still other days 20mpg. What may be causing it to change? I get the fuel at the same Shell station each fill up.

 

[Johnny G Bagwell]

I have a 2014 2500 with 90,000 miles. Driving the same route (45 miles) everyday I have noticed that some days the diesel economy may read 21 to 22mpg and other days 18-19mpg and still other days 20mpg. What may be causing it to change? I get the fuel at the same Shell station each fill up.

Computer or hand calculated?

Sent from my SM-G981U using Tapatalk

 

[Dennis Shellito]

Wind conditions. I see it all the time in my truck, and sometimes it seems like it doesn't make sense but that is what is causing the fluctuations.

 

[ramphil09]

I was using the data from the on board computer. On long road trips the on board computer has read 1 to 2 miles higher than my hand calculating. That has been pretty consistent.

 

[Knucklebuster]

I have 7000 miles on my 6.4L 2500. My fuel computer has not been reset since I got it. It seems like the average is fluctuating as quickly now as it did on the first fuel tank. Seems like the more miles I have on the truck, the slower it would fluctuate. I'm running between 14.5 and 16.0. It will fluctuate between these numbers as quickly now as when I first got it. Seems odd to me.

 

[crash68]

Wind conditions. I see it all the time in my truck, and sometimes it seems like it doesn't make sense but that is what is causing the fluctuations.

These trucks have the aerodynamics of a cinder block. Durn a minor windstorm driving down a stretch of basically flat freeway my instant read wouldn't go over 18, it's normally 22+ and the turbo boost pressure was also higher than normal. Coming back on the same road within an hour (similar winds) now the instant read was over 30 along with a lower than normal turbo boost pressure.
The wind load does the same for the trailer your towing. With my 18' boat which is 3200 lbs on the trailer my fuel economy only drops about 2 mpg. With a 24' enclosed car hauler 3000 lbs when empty the fuel economy drops about 6 mpg.

 

[jdhreiss]

It's probably the wind. I've gone from 7.5 to 12 mpg towing along the Columbia River Gorge where the wind speeds can be up to 50 mph - usually out of the east. The highway (I-84) runs east/west.

 

[Scottly]

Regen, if it's a diesel. regen uses raw fuel and mileage will tank when it runs.

 

[6speedcummins]

I stay between 21-22 MPG mixed driving going back and forth to work. When I take long trips I lock the cruise on 65 and let her go. Anything above 65 and mileage really goes down. At 65 though, I've had the trip computer read over 26 MPG. I didn't do any hand calculations but on that tank I went 820 miles, that's with the stock 32 gallon tank. Not bad for a 4 ton truck.

 

[68PowerWagon]

Do you diesel guys get a drop in mpg during the winter months? With my 6.4L I lose 2-3mpg due to the "winter blend".

 

[Fuel35 67]

Yes

 

[18Aries]

Don’t forget tire pressure.

 

[68PowerWagon]

I stay between 21-22 MPG mixed driving going back and forth to work. When I take long trips I lock the cruise on 65 and let her go. Anything above 65 and mileage really goes down. At 65 though, I've had the trip computer read over 26 MPG. I didn't do any hand calculations but on that tank I went 820 miles, that's with the stock 32 gallon tank. Not bad for a 4 ton truck.

21-22 sounds great! Is that stock, or have you done a delete or other mods?

 

[6speedcummins]

21-22 sounds great! Is that stock, or have you done a delete or other mods?

My truck is deleted but honestly didn't really make a difference in fuel economy. The biggest change with that was getting rid of the dead peddle. I do have a devise on my engine called a duramilage tuner. I put it on before I deleted the truck and it got me about 3 MPG. I still have it on running with my tune. The other thing that helps me is my truck has a 6 speed manual. I keep the RPM's low in town running higher gears, the low end torque keeps it going.