My m1009 is getingcrappy winter fuel economy 13-14mpg

[m1garand_man]

I have a m1009 that is getting crappy fuel economy. I've had it for 2 winters but this winter I'm in montana and its colder.

I usually just drive from home to work about 7miles but on the weekends I'll drie allover town and put about 20-40 miles on the truck all day. Its been in the high 20's to low 30's pretty much all the time and I put cardboard over the grill to get it up to temp faster which seems to work. But I'm only getting 13-14mpg around town. I'll admit I rarely am able to get over 35 mph. Im just concerned theres a problem

On the freeway it only gets 18.5 mpg at 65 mph.

It has a relativly new fuel lift pump and injectors I installed myself last year. and I changed the fuel filter three months ago along with the air filter.

I have been running a winter blend fuel and stanadyne fuel additive to keep things lubricated properly since new desiel dosent have high sulfer content.

Am missing anything or is this normal?

 

[Blood_of_Tyrants]

I would think that 13-14 mpg around town is about average. It takes a LOT of energy to accelerate a +5000 lb vehicle to 35 mph.

 

[raiburn]

Mine sees a big decrease in economy with the hubs locked.

 

[m1garand_man]

I havent noticed a big difference with the hubs locked. I'm just hopeing it just the cold thats affecting the engine.

It had occured to me to maybe replace or at least retime the injection pump. the scribe marks are alined perfectly but is it possible for the mechanism to slip internally?

 

[67_C-30]

I havent noticed a big difference with the hubs locked. I'm just hopeing it just the cold thats affecting the engine.

It had occured to me to maybe replace or at least retime the injection pump. the scribe marks are alined perfectly but is it possible for the mechanism to slip internally?

No not really, but the timing chain can stretch over time. That usually isn't a sudden thing though. These engines almost always perform better and get a little better mileage with the pump advanced about about .040" or 1mm. 13mpg sounds low to me, but it doesn't get cold enough here to
have to run winter blend, so I cannot comment on its effects. I've heard guys from up north say the winter fuel costs MPG, but I don't know how much.

 

[67_C-30]

Following up on advancing the pump, here's a rear wheel dyno chart showing the effects of advancing the pump. Advancing the pump .040" pretty much exactly equals 3 degress, and this is safe for the engine. It is a free mod, and 6HP and 15 ft lb at the rear wheels is very noticeable. I've done this on every 6.2 I'd had, and I've always found a little better mileage due to me not having to give it as much throttle to "go".

 

[DokWatson]

Diesels tend to be less efficient in the cold. Altitude+Cold weather+Diesel winter blend= Lower fuel economy.

 

[m1garand_man]

Diesels tend to be less efficient in the cold. Altitude+Cold weather+Diesel winter blend= Lower fuel economy.

Ok makes sense I'm also at 3000ft altitude this winter vs 50ft last year

 

[Hal O'Peridol]

Get the Stanadyne fuel additive. Works great, not expensive and will help keep your truck running in the cold.

 

[m1garand_man]

I am using the stanadyne additive. it dosnt seem to help out much

 

[2deuce]

Use 2 stroke oil for lubricity, but not for economy. Have you changed your fuel filter? that can keep you from accelerating if its clogged.

 

[thedeliverator]

x2 on the altitude + cold causing your problems. Advance the pump some and see if that helps, but know that you're not going to see numbers like you did at sea level, unless you put a turbo on it. You might run a leakdown test to see if you've got truly excessive blowby past the rings. Another (remote) possibility is a bad/stuck valve lifter, but those are usually pretty noisy....