Horrible gas mileage in sub zero temperatures

I found this article which gives some reasons for lower MPG's in cold weather. I still disagree with the idea that cold weather makes the engine run richer after warm up. It does not. If you notice the article does not suggest such either after warm up. It still maintains the same ratio but you get a larger explosion in the cylinder because the cold air can expand greater than hot air. While colder air will be denser and the system might compensate, depending on the manufacturer, by increasing the gas it does not lower MPG because it is still running the same ratio. It just takes less applied throttle to go the same distance because the combustion is greater. At best it is a wash, not a hindrance.

All the things mentioned in the article are correct as well as the person's driving habits changing because they want to get in out of the cold so they drive more aggressively. I would point out that for about every 33 amps of draw on the electrical system it takes an added 1HP to run the alternator. 66 amps and 2 HP and so on. Also in cold temps the battery loses its charge quicker and that means the alternator has to work longer and harder after start up to bring the battery back to full charge. Another thing because we are running our lights longer and using our heater on higher settings more gas is used. I have a Corolla with electric deicer on the real window. When you first start the engine and it is idling and I turn the deicer on you can actually hear the engine labor from the added electrical draw.
I would also point out the fact that a vehicle is more than a year old the sensors are not working like they did when new. Also the thermostat may have weakened and may not be bringing the engine temp up to where it should be which changes the fuel mixture. I posted an earlier article on that.
http://www.metrompg.com/posts/winter-mpg.htm
http://www.fjcruiserforums.com/forums/engine-performance/119773-fuel-mileage.html

 

Good article, that makes a lot of sense

 

Our trucks automatically turns on the a/c compressor for de-humidification of fog on windows. If you turn to anything other than defrost the MPGS go way up. I wish like other cars we could tap the Ac button to shut this feature off.

 

I have seen this claim before and it is not exactly correct. First off 134a refrigerant, which is used in our vehicles today, has the formula CH2FCF3, and a boiling point of −26.3 °C (−15.34 °F) at atmospheric pressure. That means that if the outside temperature goes below the boiling point the refrigerant in the cooling system is no longer gas/liquid, but totally liquid. If the system came on when there was nothing but a liquid it would destroy the compressor. Our systems have a thermo-limit switch that will not allow the system to come on after a certain drop in outside temperature so as to protect the system. I am not sure what the thermo limiter is set at but it is most likely somewhere around 35 or 45 degrees F above 0 degree F.
This morning it was 15 degree F outside and I started my truck and tried to turn the air on and it would not engage the compressor which is how it is suppose to work to protect the compressor. I also turned on the defroster and the same thing, no compressor. So using the defroster in cold temps does not use more gas except for the amount of electric being used which causes more pull on the engine to run the alternator.

 

if you leave it idling, that's not going to help

the other thing is, it will also idle higher until the cats warm up

 

Do you use synthetic oil ?
That will help engine runs smoother on startup or short trips when your engine hasent had time to fully warm.
I also find 93 octane helps a bit.
But don't expect better than 12-14 mpg in these conditions, in my experience at least.

 

Does anyone have experience with changing differential fluids to synthetic and winter mileage? It's consistently below 0 for a few months in a row here and I get anywhere from 10-12 MPG in the winter time. I attribute a decent amount of that to warming times but I still feel like it is rather low. I have noticed that even when driving in 2WD the truck has a hard time coasting (loses speed rapidly without using the throttle).

I run synthetic motor oil, but have not changed the fluids in the differentials or transfer case yet (truck has 22k).

2010 4.0 DCSB

 

I'm not sure I saw it above, but don't forget about winter fuel blends giving worse mileage. I'm attributing my lower MPG's to:

Winter Fuel
More Idling / Warm up time
Staying in open loop longer (takes a lot longer for my TC to lockup)
Cold oils (yes synthetics help)

I don't know if it's ever been studied - but since cold air is denser, how much more effort does it take to push the truck through the air???

 

When I lived in Alaska, there were power outlets in all the base housing parking lots and a lot of other places. This is for a reason, engine heater. Personally, if I live somewhere that it was below freezing every year, I would get one. I don't remember the company, but there I one who makes kits that include engine oil pan, trans oil pan, and a freeze plug style heaters. Using that your engine and trans will be ready to go when you start it.

 

MPG drop significantly in the sub zero temps due to many factors:
1) winter gas can make a 1-2 mpg difference between winter 87 and summer 93
2) engine knocking in cold temps low rpm means its not running as efficient as it can be
3) even though your engine is warmed up doesn't mean your trans is up to temp. rough shifts, holding gears longer increase fuel consumption.
4) don't forget power steering pump, it draws more power from your engine to move sluggish fluids.
5) cold temps decrease pressure in your tires. more area= more rolling resistance
6) tire compound. the colder it gets the less the rubber wants to flex. = more rolling resistance.

the argument about colder air producing more power is correct to a point. but it is not an absolute inverse correlation. It's true down to a point of diminishing returns. Which is likely above 0 degrees F.

not sure about the aggressive driving argument... cold weather makes me drive more cautious so i don't end up in a ditch stuck in sub-zero temps for hours..... depending on weather

im sure there are other contributing factors these are just some things i noticed besides the 11mpgs i was getting

 

How long do you warm up? Idling kills my mpgs

 

Of course it does. 0mpg when idling...

 

A couple of minutes, enough to get the oil flowing. Then start off slow, not pushing it for a mile or two. They warm up faster going down the road anyhow. Currently getting 16-16.5MPG. I get 20+ summer. I run 91 octane, 0% ethanol. Synthetic lubes, secondary air filter delete.

 

Oil flows in the first five seconds.

 

Prove it.

 

The oil light would be on if the oil were not flowing. In fact it does not even take 5 seconds. Just cranking the engine before it starts, starts the oil flowing. There is no need for a warm up other than personal choice. Also the valve train would be chattering like crazy and the mains and rod bearings would be gone after a few starts. If the oil was not flowing immediately it would not make any difference if you are moving or setting still the damage would happen.

For those who are getting lower MPG's because of low tempts they can use one of these which would easily pay for itself in less that a winter and for some in one month or so.
http://www.realtruck.com/fia-winter-front-and-bug-screen/

 

This problem eventually goes away on its own when the Delphi A/C clutch comes apart like mine did

 

The motor spins, the oil pump turns, oil circulates. I would accept any legitimate argument against this fact.

The oil pump doesn't have a clutch, does it?

 

The oil flows, just not as easily because it's "thicker" when cold - especially conventional oil. So it takes more force (I.e. drag) to pump it until it warms up and thins out.

That's one benefit to synthetic, it flows better in extreme cold.

 

It is cheaper to run synthetic than to idle...