I know that winter fuel does affect fuel, but I have some observations that don't click with it. My mileage dropped off lately as the cooler weather settled in. Winter fuel? Thats what I thought. But we had a 74 degree day followed by a 70 degree day and guess what, my fuel mileage went back up.

The winter economy loss has done that with a different engine, a different electronics system, different injectors, sensors etc. Now I am wondering what the deal is. I have always believed that cooler intake air contained more oxygen, hense more power and economy. This is not the case with the Cummins. Is it possible that the cool air intake in the winter is detremental to the economy? Possibly the oil is cooler thereby thicker. Something in the Cummins ISB causes the loss of 1 to 1 1/2 mpg below an average temperature of 50 or so.

I got over 12 with loads through two different fuel suppliers in the last two days. Tomorrow the temperature is going back down and I will suffer the loss as usual. I will get around 11 on the best average. I don't have any figures to make a comparison, but I think the truck loses a little power in the cooler temperatures also.

I have spent some time with the EZ and its settings checking fuel mileage. Common sense tells you that less smoke is better fuel mileage and I have a smoke problem with the highest setting sometimes. I have found that the best economy seems to be with the smoke though.... looks cool too After the engine has been shut down to load, especially at night, the first hill I pull going through the gears, really fogs the cars behind me out. Not much at road speeds.

 

I've been wondering the same thing about the cold air being to cold. I closed the hole up in my scotty for this tank to see what happens. My truck does the same thing your's does. I'm in southeast texas and I'm pretty sure that we don't get winter fuel shipped down here. I'm guessing this engine is doing it's thing for ya? Glad to hear you finally got everything fixed and working right.

 

Blue this engine is really great for pulling freight. Not so hot for hot rod stuff, too low a governed rpm. Still chasing a darn oil leak, but all else is running great. Over 50,000 on it now. I did have to change the head gasked a couple weeks ago, was leaking antifreeze.

 

Awesome. At least it was just a headgasket and not another block.

 

Mileage is affected by temperature, humidity, barametric pressure, wind, tire pressure, and extra weight in the vehicle.

Air up the tires, slow down 5 MPH and you'll see a big difference.

 

I am talking about a 30,000 gross weight. Many times slowing down will hurt economy, depending on the lay of the land. Higher speed coasts over hills that you have to work to climb at a lower speed. Wind will always kill economy, from any direction. This was not a thread to discuss getting better economy, just the difference in temperature affecting the engine. And any possible changes that might help eliminate the effect.

 

I also see it, 2 weeks ago or so, we had some nice warm weather, 74* days, nice and sunny, I hit 19 MPG, and couldn't believe it, now we hitting 50* in the day and I can tell a big difference in MPG. No idea what causes it, has to be the air temp, but you would think by the time it hit the motor it would be warm.

Clint

 

You southern boys should see what kind of milage you get when its -30....

 

I think what kills my MPG is the cold morning start ups, on the overhead ( I know it's worthless but..) I will see 18 MPG, and within a mile of being easy on it till she warms up I have dropped to 16.5 MPG, after the trucks warms up the MPG picks back up, but not to the nice warm sunny weather economy.

I'm running Rotella synthetic oil (or the so called synthetic), if it's from the oil be thick from colder temps I would think once the motor temp warms up the oil would also ? Well I will try something different soon on oil, I can't handle the smell, it's like rear end dope on the old trucks, ya just keep smelling the stuff, a little whiff here and there.

So what's making these trucks consume more fuel in colder weather, and I don't think it has anything to do with the winter fuel either ??

Clint

 

You might be on to something Haulin. I run "arctic diesel" in my truck almost exclusively (which is straight number 2 with an anti-gel package) which is not supposed to have the normal winter blend drop in mileage. But I see an immediate 3-4 mpg drop when the temps start to get low. I thought that maybe the fuel claims were BS, but maybe it is the truck's programming.

 

I'm debating on putting my stock air box back on to see if that brings the mileage back up.

No thanks. You can keep that up there.

 

ive noticed it a bit to. how about any of you guy with winter screens on, does your milage stay the same? heres a random thought, cold air = denser air = more resistance?

 

How about colder air, resulting in more oxygen, resulting in a leaner mixture or ratio of burn. I also am wondering about cooler fuel doing it. In the warmer weather the tank heats up some, but the cooler weather it does not.

As mentioned before the warm up is not it, I generally run through three or four tanks with little shut down time. The second tank would not be affected.

I used to think I was getting poor fuel and/or the winter fuel problem but recently have realized that it is tied to temperature. It should pick up some as the air is not on, anything above the 50's I have the air on even if a little heat is added. I really like the dry air feeling and the fresh intake.

I just though of one, I have not looked into, I know cars that are computer have an outside air sensor, do these? That might be the culpret.

I do know that the warmer it is outside the more the truck smokes, so there is some difference in fuel supply.

 

there has to be something with the Winter weather and mileage, this is sorta insane but,

i was pulling 17 mpg usually

and now im down to 15... under same circumstances, just in cold below 50 degree's weather...

maybe the cause is, ive been feathering the go pedal a bit to much and the engine doesnt even heat up all the way on a 15 minute drive

AND WHERE THE HECK IS MY SNOW AND MY BLIZZARDS, i miss when the banks of snow in Illinois would get 6 or 7 feet tall.

i know you guys do

now i get to see it snow 1 day, then melt the next and then start pouring out for a week!! :/

these mild winters are getting a little odd.

 

Oxygen is still at ~21%, and the density issue isn't enough of a change to make a really significant impact on mileage. Even for drag racing, the difference in HP, ET, and top speed is minute fractions that aren't significant for the parameters we look at. I wonder more about the viscosity of the fuel in cooler weather? I have actually had better mileage with the 50/50 winter blend I bought last tank than I have had with the three prior straight #2! I am not really sure what the 50/50 blend is, either. There is exactly one diesel pump in our town, so choice is limited.

We have an 80 ton/day Cryogenic Oxygen Plant at work and do not make any more liquid oxygen per unit of air in cool temperatures than we do during the hot summer months. The difference is in our Oxygen demand during cool weather vs. hot weather. The fractional distilation of air to liquify Oxygen gas is where I have the most experience with Oxygen "concentrations" at various ambient temperatures.