Heat and the 6.2

[Barrman]

Last summer, I was getting 19-20 mpg in town with the M1009 on stock tires. 20-23 mpg all highway with the stock tires. The 23 mpg run was 430 miles and the outside temps were 107°. Speed never exceeded 64 mph and normally 62 mph gps was my cruising speed.

Winter, such as it is in Texas, came along and my in town mileage dropped to 17-19. I put the 33 x 12.50 BFG A/T tires on in December. Mileage stayed in the 17-19 range in town. (Adjusted for what the gps says is my correct distance covered. 6% is what my odometer is slow.) Never got to make a full non trailer pulling highway run. Still got 17.9 pulling a pretty loaded M101 500 miles though.

Spring had the temps up but the 101 was always attached when I went anywhere far. Never got over 18 mpg on any tank. I also tried to do a few 62 mph mileage runs without the trailer but always ended up in a hurry and running 65-75 to keep from getting run over on the interstate. Again, never got over 18 mpg. More 16-18, actually.

Summer is here in full force now. I drove 94 miles Tuesday with outside temps in the 90° range. The truck felt like it had more pep than it has in a long time. I was at a teacher conference, so I had to leave in a hurry for food a few times a day. All on interstate access roads which are get to speed in a hurry, stop, get to speed, stop, repeat. Then I drove home yesterday at 65-70 mph. Topped off the tank and 18.4 mpg. Not my best, but my best at that speed.

The idle is also up a little.

Now that the back ground is all listed out supporting my idea. My question is do NA diesels like hotter air temps? I grew up in the gasoline engine world where colder/denser is better. It seems contrary to physics, but my numbers and seat of the pants feel all support the idea that the 6.2 runs better and is more efficient with higher out side air temps.

Any body else getting a better running/performing truck with the higher temperatures?

Oh, the diesel in this part of the country does not change with the seasons as far as I know.

Thanks.

 

[patracy]

It's a combination of warmer engine temps helping combustion (not intake air temps though) and the fuel. Winter fuel typically has more #1 diesel or Kerosene mixed in it to help combustion. These trade off BTU's though.

 

[corelokt]

Mileage will always better warmer than cooler. Winters here see 40 below fairly often and the diesel will hardly light. Have you run any 2 stroke oil with your diesel? Makes a big difference.

 

[ken]

I have noticed with all of my 6.2's both civi and CUCV's. They dont like cold air. And a 2 to 3 MPG difference is normal for my 82 civi with a 6.2 and banks turbo. My CUCV doesent get milage checked very often because i use it off road enough that there will be no accurate numbers. And they both run smoother above 60 deg. I have replaced the thermostats with 180's. It gets too hot here for 195's I don't need any overheating. for slow moving of roading

 

[GFB]

Winter fuel. I lose about 2mpg in my dodge cummins during the winter too, but the newer engine is actually more responsive in the winter because it adjusts timing for the colder intake temps.

 

[Boisemed]

2 stroke oil?? how much do you add per tank and is this for normal driving or only Winter?