does gas mileage suffer in cold weather?

[b56tc]

The last 2 tanks I'm driving exactly the same profile and route with about 1 - 1.5 mpg less average. It has been consistently single digits to mid 20s, dry pavement. Logic says mileage should improve - colder denser air, cooler engine operating temps ie more efficient engine; but less mpgs. Anyone else with the same observation?

true confession for this question - about 2 weeks ago (2 tanks of gas), I drove my rig semi-comatose at about 3800 rpm for about 8 - 10 mi before I figured out I was in 3rd gear at 70mph; I'm paranoid I jacked something in the engine. Not fun confessing your stupidity. A testimony to the quietness of the engine and cabin? nope, I was just half asleep. Idiota.

 

[slinger5150]

If its cold and you have the front window defrost on, its running your A/C compressor to pull any moisture off the front window. That'll cut into your MPG same as having A/C cranked in summer.

 

[cruiser88]

im getting better

 

[NMuzj100]

You have ethanol in your fuel. (Winter Blend)
Shorter days = more headlight time
More energy required to turn AT,Diffs,TC until oils are up to temperature.
More rolling resistance from stiff tires and effectively lowered tire pressure.
Less efficient road surfaces ice,snow, sand ect..
More stop and go caused by bad conditions and reduced visability.
Seat heaters, rear defrost, and AC compressor from defrost all steal energy.
Richer fuel mixture until engine is up to temp.

You also get fuel "shrinkage". The fuel comes out of the ground at say 55 deg and then into your tank where it cools to say 10 degrees. As it cools the fuel volume shrinks (although the energy value remains the same). The opposite of what happens in the summer when the fuel can expand and cause problems.

And a cooler engine is not more efficient. Hotter is more efficient until you start to damage components.

I do notice a benefit to premium in the winter that I don't see in the summer. It may be that the increased air density allows the engine to really take advantage of the higher octane in a way that I don't notice in the summer months (perhaps due to altitude 7300ft ASL).

I don't think 3800 rpm for 10 minutes is any more damaging than 20 minutes at 2000 rpm. So I would not worry about it.

 

[stevek]

Winter blended fuel will also tank your milage. On my 100 I go down about 1mpg in the winter. There is also a fair amount of 75w90 gear oil in your diffs that gets pretty stiff in the winter when you first start out!

 

[Jim_Chow]

I also always get better fuel economy (by 1-2 mpg) in the summer. This goes for all three cars (86 4runner 22re, 01 honda prelude, 03 LX). I attribute the difference to less efficiency before the engine is warmed up (in the summer, it's 105F outside, no warmup needed), plus I'm guessing the cooler, denser air means the EFI can add more fuel while with hot, dry air, the mixture will be leaner. Any truth to this? We are using the same gas (10% ethanol) year 'round now.

 

[DoctorJay]

The only thing to add is to watch the coolant temp gauge. If you have a thermostat that's stuck open, the engine may not warm up enough and keep running with a rich mixture -- which will cause your mileage to drop a lot.

 

[aljordan]

There are less BTUs in winter blended fuel compared to the summer blends. This attributes to most of the difference.

 

[Martin White]

I have nearly 30 years of data on all the cars I've ever owned. Without exception, every vehicle I've ever had, and everything I've read, suggests fuel economy gets worse in the winter than the summer, usually somewhere between 5 and 10% worse.

 

[drsales]

Besides btu of fuel, air density has also changed thus harger to push the sleek design thru the thicking air. Plus the earth has rotated on it's axis towards the south which requires more uphill driving!

 

[b56tc]

interesting opinions

to elaborate on them: the truck is in a heated garage; starts out the day at least with warm fluids and tires; no slush and crap to drive through until last couple of days when it snowed again. But good thoughts.

so - my mileage is back up to 16 again. Weird, weird. I had never had such poor mileage until after that high rpm run; then 2 tanks; bad gas? Or like we say with aircraft that are fly-by-wire (no linkage anymore, just capacitors and sensors), "all it takes is one queer electron...."

I think the thread was really driven by guilt at my stupidity. And once again, I survived myself.

thanks for the ideas

56

 

[SWUtah]

I agree, got 12.5 the other day on 91 octane. I normally get 15. Temp's around here have been -10 windchill.