Horrible gas mileage in sub zero temperatures

I know there's quite a few mpg threads but I haven't found one regarding cold temps. Anyway..

It's been below 0*F the past few days and it seems like I've been getting less than 10 mpg. I understand that low temps reduce gas mileage, but should it really be this terrible? I've got a home stock TRD dcsb V6. Thanks in advance, Bill.

 

Shouldn't be the case if you don't spend too long warming up the truck. Make sure your tire pressure hasn't fallen low because of the cold. Remember the tires lose 1 psi for each 10 deg F drop.

How are you measuring mpgs, odometer+pump reading between fill-ups, or by OBDII output?

 

If most of your trips are shorter than say, 10 miles, that number isn't surprising. One also idles a little more in cold temps, and an idling truck gets 0mpg. My consumption usually goes down 20% in the wintertime.

 

I usually let it idle for maybe four minutes in the morning so it get get to 50*+ before I drive off. Most of my driving is less than ten miles. Judging by the odometer and fuel gauge I know that my mileage is way way lower than before, like 1/2 my normal mpg.

 

Ditto

 

I always thought that cold air temps actually improve 'performace' (milage may be different) on an internal combustion engine..... the air is more dense that warm air.

.... True?? Anyone??

 

Our trucks are heavy on fuel especially cold starting. And take much longer to get warmed up if your driving short distance. Basically the colder the engine temp the more fuel you will consume. Theres nothing that is going to cure it. My best suggestion is to get a ultra or scan gauge to monitor temps, average mpg, etc. Then you'll have a better idea whats going on.

 

Yes, performance does improve with the cold dense air.

Its also pretty normal for milage to bomb with short trips in cold temps - richer mixture and the fact that it will stay in open loop pretty much the entire trip as the coolant temp will barely reach normal by the time its shut off. Combine that with tire pressure dropping off in the cold, cold (stiff) tires, and the stiff, cold gear oil in the diff(s), t-case if a 4x4, and transmission, and 0mpg warm-up time, its a noticable difference. Switching drivetrain fluids to synthetic helps a wee bit. Personally, I've seen a 30%+ increase in fuel consumption with short trips in the cold. A block heater with a timer helps some too, have it come on 3 hours before you're going to start the truck.

 

According to my scangauge, my truck is only in open loop mode for the first two miles or so, no matter how cold the weather.

Don't forget, even if the motor "might" be more efficient in sub zero temperature, consider how thick all the lubricants are in those temps. Every bearing on the truck is almost frozen solid...

 

Cold temps should not lower MPG. In fact cold temps should increase the MPG because the intake air is colder which increases compression. Long warm ups will lower MPG. Also if your thermostat is bad and not bringing the truck up to manufacture recommended Temp the truck CPU will stay in warm up mode which uses more gas.
Here is an article about a FJ having this problem
http://www.fjcruiserforums.com/forums/engine-performance/119773-fuel-mileage.html

 

It's normal in all vehicles for mpg to drop in sub zero temps.

 

you are correct sir - cold air improves performance and requires more fuel to maintain the a/f ratio. the a/f becomes lean / leaner as the air becomes colder. The ECU will add / subtract fuel to maintain a target a/f ratio.

Cold air requires more fuel and hot air requires less to maintain the same a/f ratio. but there is much more than cold air at play in sub zero temps. the ECU will lower the a/f requiring even more fuel, retard timing, etc..

 

I've currently got my phone app to show engine temp, intake temp, a/f ratio, MAF, and a few others. All readings are normal. I just added the average mpg meter so I'll keep an eye on that.

On a side note, I highley recommend the phone app 'Torque'. The app is $6 and the OBD2 Bluetooth adapter was $30. It allows you to setup 5 pages of reading to setup, records min/ max, and has 100+ readings to choose from(not all work with our truck).

 

This last week it was around -45 in Fairbanks I'm lucky to get 150miles out of a tank. Thinking of driving my old 4runner when it gets cold.

 

My 07 4.0 is thirsty year round the fuel gauge is constantly on the move it is over maintained with synthetic everything. Always has clean everything and new plugs all the time. I run my Grandprix to and from work 25-30 mpg and use the Tacoma when I need to I love the truck but the mileage is awful and it took me quite some time to fess up and realize it is what it is.

 

Just filled up my 06 sport tonight and checked my MPG a whopping 12mpg... It's been cold past few days though, had 182 miles on the tank... And 61K. On odometer.... I always see a decrease in the winter...

 

My truck ran 19mpg during the summer months, right now it's running around 16mpg... My GM mpg is worse in the winter also.

tsb makes a great point on the reasoning.

I've also heard some posters state that fuel mixes are changed with regards to additives since fuel is less volatile in colder temps, but I haven't researched the validity of oil companies actually doing so.

 

I learned the other day that when you run the defrost the a/c runs and therefore reduces your mpg's even more. I'm actually in the process of gauging my mpg's while limiting my use of defrost to see if it even changes at all. I also recently changed to all synthetic in the diffs and transfer case, seems smoother but we'll see what happens.

 

I personally understand how the mileage goes down when cold, many factors.

But the only reason I bought my truck was for how it performs in the snow and cold

not for the MPG it gets.

no matter how bad the MPG, its worth it knowing I will make it home safe and sound

in the worst of winter conditions.

 

I average 20MPG in Summer 19 MPG in Winter with my '07 2.7L.

Summer I get tanks from 20 to 21 MPG.
Except towing gets 14 to 15 MPG. (3200 lbs / single axle / 6' x 10' enclosed box trailer)

Winter I get tanks from 18 to 20MPG.
Single digit positive and subzero gets 18.X MPG.
Warmer teens and 20s (fahrenheit) gets 19 to 20 MPG.

EDIT: No complaints.