Why is my car getting bad gas mileage now that it is cold?



I just moved to Washington DC a month ago from Phoenix, Az. I drive a '99 Toyota Corolla that runs great and normally gets excellent gas mileage. I have new tires on it and got a tune up the day before I drove the car to DC. I have also recently filled the tires with air.

So what can I do, now that I am in a cold climate, to get better gas mileage? Do I need the carb adjusted? Please advise.


There is no carb to adjust. You have EFI, and the computer has already adjusted itself to the different conditions. Your going to use more fuel in the cold, and you’ll just have to live with that. The car will run rich as the engine heats up, and may continue to run rich if other conditions prevent it from warming up completely. If it’s been a while since the last time you had the coolant flushed and filled, with the thermostat and radiator cap replaced, this may help.


I just returned from a 350 mile trip from a southern state. When I left, the temperature was 46 degrees and our Toyota 4Runner was getting 25 mile per gallon on the interstate. As I got further north, the outside temperature dropped to 32 degrees and I was getting 22.5 mpg. Cold weather and lower mileage go together. Gasoline is also blended differently for colder climates. In a colder climate, the gasoline is formulated for quicker starts, which makes for lower overall mileage. There is nothing you can do about your car. It doesn’t have a carburetor (and you wouldn’t want one) that can be adjusted. It has fuel injection that is controlled by microprocessor for optimum mileage.
Your best bet is to follow my wife’s suggestion: Move where it’s warm. She says that if we did this, our Toyota would get better mileage and we could see our grand daughter more often. I would have to give up my job and go on welfare to do this, but on a teacher’s salary, it probably wouldn’t make much difference.


All the lubricants are thick and stiff. The tires rolling resistance is much higher. Electrical loads are much higher (heater, rear defroster, headlights, wipers…) and DC traffic…


OP moved to a much more congested area with more stop and go driving. That also affects gas mileage for the worse.


Thanks to everyone who gave me their input. I did move from a hot climate to a cold climate but was not prepared for such a radical change in MPG on my car. I guess it is a sign that I need to use the Metro more often.


A factor related to the others mentioned here is the time an engine takes to reach operating temperature (~190 degrees) from ambient temperature, whatever that may be. An engine is cooling while not in use, and if it has enough time, it eventually reaches ambient temperature. In Phoenix in the winter, after sitting overnight, your engine may be warming to operating temp from an ambient 55 degrees, but in DC, from 20 degrees.

By design, engines run richer during the warmup period, until they reach operating temperature. The longer that warmup period, the lower your average mileage will be.

You lengthen that warmup period if you turn on your heater right away instead of waiting until the engine reaches operating temp.


I’m guessing that you got 34-36 mpg in Pheonix and now you are getting 26-28 in DC. This would be expected for all the reasons stated above.


Does DC switch to a winter blend gas? There is less energy/gallon in the winter blended gas due to higher oxygen content. Our highway mileage drops about 5% consistently in our vehicle due to the winter blend.


Some other things to mention:

New tires consume more fuel that worn out tires - all other things being the same.

There can also be a HUGE difference between tires.

But personally, I think the real difference is in the stop and go traffic. The fact that the Metro is an option says this is very likely.