Is it normal to get worse gas mileage in cold weather?

I drive 40 miles each way to work every day and always keep track of how many miles I get on a tank of gas. It seems every year I see a drop in my gas mileage by 2-3 mpg around October/November. By April/May the mileage goes back up. I live in southeastern Ohio and have pretty much all four seasons. I have only come up with two possibilities.

1. The air temp sensor notices colder (and more dense) air so it increases the amount of fuel introduced into the cyclinder to maintain the proper fuel/air ratio.

2. The gas stations switch to oxygenated fuels in the winter. I researched that while oxygenated fuels have the same octane value their energy value is less. Could the computer be somehow compensating for this?

I am very consistent with all of the normal maintenance items. I have only 50K on the truck and have been very happy with it. This drop in gas mileage has me puzzled though????

2001 F-250SD 4x4 w/ 5.4
Only mod so far: K&N air filter

 

There could be a couple of factors involved. If you let it warm up some before driving, this will decrease mileage.
The colder incoming air could require a little more fuel.
The winter fuel has more alcohol in it which makes it tend to evaporate faster.
I live in a county with reformulated gas. I can drive 14 miles and get non formulated gas. I do this because I consistantly get about 2mpg better mileage than with the reformulated garbage that they sell here. It also goes bad in about 4 months compared to regular gas.
Jimmy

 

Here's a thought, the AC dehumidifies the air when placed in any position other than vent or floor (iirc) this is why the newer vehicles defrost the windows quicker and they stay that way. This extra load is like placing your AC in the on position. My truck does the same thing, it's seems the defroster is the culprit. The reformulated gas could also be a contributing factor.

-Kerry

 

dfknaus:
I believe that it is very normal for your mileage to be less in colder, winter type weather.

Think way back when engines were carburated. The carb choke would engage on a cold start to allow the engine to run on a richer mixture. If the choke setting was set too lean, the engine would stall and back-fire through the carb. After the engine reached a certain temp the choke would kick out and the air/fuel mixture would be less rich...using less fuel.

On today's engines, the computer controls the air/fuel mixture. A cold engine in the year 2003 is still going to want a richer mixture to run on until the engine is warmed up...more gas less air. (tastes great less filling?) lol

Living in michigan, this is a fact of life...more MPG's in the summer vs the winter. I see between 2-3 mpg drop in the winter as you do. And I don't sit for 20 minutes letting the engine warm up before i drive away either.

I would bet that if you lived in hawaii your mileage would always be the same year round. Just my 2¢ worth of blah blah blah!

-hooD

 

I live in Hawaii and I get about 15 mpg year round:-)

 

Boss Man,

Just a thought and my 2 cents: if you have a fail safe thermistat it may be stuck in the open position. This will not let your vehicle get to normal operating temp and the fuel system continues to operate in cold mode (rich air/fuel mixture).

Does your vehicle have a temp gage and if so does it move?

 

Mine has dropped about 1.5mpg too since the colder weather hit. I believe that the engine runs a little richer due to the cooler air passing over the air inlet temp sensor. Also, the winter fuel blends have more alcohol in them to keep them from freezing, but it also evaporates quicker. I use the floor setting only on mine, so the a/c compressor doesn't run. I do occasionally run it to keep the seals from drying out, but mostly just run it on floor or vent.
Back down to about 12.5 mpg.
Jimmy

 

Don't get me wrong, Jimmy. The compressor does run, just not under the same load that it would if you had the Defrost on High or AC on MAX. Had more than one person tell me that I was wrong... but only technically . So the compressor does move, since the serpentine runs through it, but it doesn't cycle quite like an AC unit would under load.

Along the lines of serpentine belts (since we pretty much summed the majority of the MPG loss to winter fuel blends and cold air) what about the alternator load increasing with the fan and lights running more (longer darker, colder nights)? Small loss at best, but it's still a drag on the engine.

SO, we've determined we should all move to Hawaii!!!

-Kerry

 

That sounds like a plan, I may need to lift the truck some to drive it across the ocean though!!!!

 

You might get better gas mileage here in Hawaii but you will pay $2.09 a gallon for your fuel. It's worth it for me

 

Put a can of "Complete Fuel System Cleaner" on a nearly empty gas tank then fill it up ,dont buy a cheapo brand, i use the Slick 50 brand, about 9-10 bucks, after the tank is nearly empty change your fuel filter. (Fuel filters must be replaced every 12-15,000 miles just like your tranny oil. Also check your tire pressure, for every 3-4lbs of tire pressure missing you're losing 1 to 1.5 miles per gallon. Hope it helps.

 

Tire pressures are at 35 as required. I ad a can of Outlaw Truck and SUV. complete fuel system cleaner every 3000 miles at each oil change.
Jimmy

 

Good I thought I was the only one getting lousy mileage in recent months. Just another cost of skiing.

 

While I have only 6000 miles, I too have noticed a 2 mpg decrease in mileage. I thought it was because of the bug deflector I put on, but I think it is the weather and the ethanol in the fuel. I also use the remote start and leave it running during all my short stops throughout the day.

 

Ihaven't figured this one out yet myself, my previous truck was 02 f150 FX4 5.4 triton bought new about 1 1/2 years ago my first tank of fuel i got 13.9 mpg. after each tank after that it steadily went down from there to an average of 12.5 around town. I live in South Florida i frequent north Georgia Atlanta area and get 14.5 to 15 when there. Now here is the kicker i recently purchased a 04 f250Lariat FX4 5.4 triton. and the same thing has happen. First tank was 13.9 and by the 3rd tank i'm down to 12.2. Since i received my new truck with a full tank of fuel and didn't know how full it was filled i filled this truck until it was over flowing. I'm not complaining it just puzzles me and i gotta admit 13.9 sure would be nice to see again.