my truck has taken a dip in mpg. Does bitter cold weather effect diesels? I went from 21.5 to 19.5 mpg when *edit* blended fuel came out in Nov, that was expected, it's always done that. This last tank was 17.4 tho, and looks like I'm on track for that again. I checked for leaks, and I'm not dumpin fuel into the crankcase, and the lift pump is a couple months old. (I was still getting the 19.5 mpg with this lift pump at first, so I don't think that changed anything)

I know gas motors do worse in the bitter cold we've been having, but I guess I didn't figure diesels would? I really have no idea tho

 

You will have a noticable diff. in the winter months with blended fuel

 

yes, I expected the drop from 21.5 to 19.5 in Novemeber. I've lost another 2mpg in this bitter cold weather that I didn't expect. Another point: I buy fuel from 3 diff. stations depending on when I need it, and that has never effected mpg in the past, so I don't believe that's a problem now either.

 

I wouldnt worry too much I only get 14-16 mpg. Mostly freeway (75-80 mph) Maybe my truck has a problem . Any thoughts or is this normal for these speeds . Thanks in advance. BTW this is in my '93.

 

RAM,
thats about what mine gets.

 

well, it's not the actual mpg as much as the sudden, measureable change. I don't know about y'all, but my truck never changes. You drive it the same way and it always behaves the same way. Any deviation makes me nervous

 

Did you rmilage change with your new tires? I would check tires/pressure, engaged front hubs, bad U-joints in the drive shaft, in about that order.

If you drive shorter trips, and slower, then things like thicker oil in the transfer case and rear differential can have an effect when it is bitter cold.

I doubt it is the injector pump dying or anything like that.

 

heck, my 93 d250 club cab only gets 16 city, and I"m in California!

 

hmmm.....tires, that's interesting. The first tank back from putting the new tires on I got 19.8, but only 1/2 of that tank was on the new tires. Geez, I wouldn't think those yoko AT's would drop 2mpg over the highway tread I was wearing.....

I have them a little under the recommended psi (55 vs 65) to help with the ride. It looked like to me that they were making a nice contact patch, if even a little light on the outside, so that should mean they had plenty of air in them. It's worth a shot to go up to the 65psi tho, I can take the ruff ride if it gets my 2mpg back

I've been running with the hubs engaged some of the time, depending on the weather, but less often then I was with the old tires.

 

If I recall correctly, tires are almost as important as wind resistance to fuel milage, and the realtionship between tread design and speed is such that over about 55 mph the impact gets bigger quite quickly with speed.

I would think the key is AT vs. highway treads. I would be curoious, though, to see if the inflation makes much difference.

Good luck,

Alec

 

I am losing a couple of mpg and blame that on the bitter cold
( -20 to -40 C ). I have a hand throttle which I set at at a higher idle in this weather and will let it run longer before putting it in gear or hopping into the store for a min or two. That combined with a drop in combustion efficiency when cold contributes to my loss.

 

maybe it's a combination of the 2. I too have had to let it high idle for up to 10min a lot of the time leaving work to get any heat built into the oil. And the truck is working harder during the warmup period (as seen on my pyro and boost gauge). The tread theory with wind resistance is very interesting...these tires do grip much better than the old ones, maybe that's the price I have to pay for it

 

I have 2nd gen friend at work that had his mileage drop a couple when he put on aggresive tires.
Also 2 to 3 mpg drop for winter fuel is normal.
Jay

 

Remember that blended Diesel is a mix of #1 and #2 - #1 does not produce as much BTU's as #2 therefore you will use more fuel to get the same bang for your buck.

Bob