Is my car's fuel consumption affected by hot weather, and if so, how? If it is important, I drive a diesel car

Answer 1

Depends on how hot the weather is, of course.

In nearly 40 years of driving and tracking my fuel efficiency, I have found that, in general, my car gets better gas mileage in hot weather than in cold weather. This can be attributed to a number of factors:

An engine at proper operating temperature runs more efficiently. In cold weather, it takes longer to reach operating temperature, so the car runs less efficiently for longer. Most often you are also bleeding off heat for the cabin of your car. And you really kill fuel efficiency if you fire up the car and let it sit in the driveway to "warm up".

Short trips -- such as stop-and-go traffic to the office or errands around town -- also reduce fuel efficiency, as opposed to long trips at consistent speed (many cars are at their peak fuel efficiency at about 55-60 mph) on a freeway with few stops/delays.

On the other hand, the other posters are correct: if you run your AC during hot weather, you add a tremendous load to the engine, dramatically reducing fuel efficiency. So, if you can handle the temperature/humidity outside, it is most efficient to drive in the summer with the windows down using "4-55 Air" -- four windows down and driving 55 mph!

For some specific examples from my own experience driving my current car (a 2001 Oldsmobile Alero, 4-cylinder, 5-speed manual transmission):

Winter best mpg: 31.40 mpg
Winter worst mpg: 24.15 mpg

Summer best mpg (no AC): 36.68 mpg
Summer best mpg (AC): 33.59 mpg
Summer worst mpg: 26.88 mpg

Answer 2

As has been stated already, hot weather leads to things like AC operation - however, just having the windows open will increase fuel consumption by increasing drag. Another possibility is that air density changes with temperature - so the induction system could possibly be affected by having warm air even when starting the engine from cold. People, of course, get bad tempered when driving in hot weather - which leads to aggressive driving and rubbish fuel consumption. Take pleasure, the next time you see a road rage idiot, from the fact that he is paying for his pathetic tantrums through the pumps!!!!!!!!!!!!!

Answer 3

Driving a diesel car the only affect hot weather has on your car is the fact your engine is getting hot air which makes it a little less efficient but not terribly. The who AC thing is a lie. you turn on the ac you might get a 10% loss the exact same as if you drove with your windows down. the only way to fix that is no AC windows up.... I don't think that's a feasible alternative.

Answer 4

Yes it is but you proably wouldnt be able to measure it:

1) Colder air is more dense so your car can potentially burn more fuel in the greater mass of air which could be drawn into the cylinder. If your vehicle is fuel injected it is unlikely that the system compensates for air pressure so there will be little difference. A carburated engine will theoretically have more power, but will be burning more fuel and be no more efficient.
2) Colder air is more dense and will therfore cause more friction as you travel through it. (Thats why passenger jets fly at high altitude in low pressure air.)
3) Diesel will ignite more readily at higher temperatures. Normally your car regulates the ignition temperature using it's cooling system. Your engine will be more efficient by reaching optimal temperature sooner on warmer days.
4) Air conditioning is more efficient than having the windows down at high speed. At low speed having the windows down is more efficient.

Points 1,2 and 3 are unlikely to be measureable however careful use of air con will make a difference. Driving more gently, avoiding braking and reducing speed will make the most difference.

I used to own a 50cc moped which I tuned to run on high octane petrol and travel at 70 mph. It's maximum speed varied more through atmospheric pressure (about 4 mph) than thorugh temperature. There was no measureable difference in fuel consumption.

Intake air filters can be affected by moisture in the air because wet air limits airflow by condensing in the filter mesh. This effect reduces our companies gas turbine efficiency by about 2% and has a direct impact on efficiency.

Answer 5

The exterior temperature has little to do with the fuel consumption of the engine once it is warmed up. Turning on the air conditioner (or any engine powered gadget for that matter) puts an increased load on the engine that is not directed towards moving the car, so more energy is expended per mile.

Answer 6

Well, jplrvflyer had it partially right... it is true that when the air is colder there is a higher density of oxygen so you will have a more complete burn of the fuel in your engine, but the part he's missing is the carnot cycle. In reality your engine is only about 20% efficient at burning your fuel, and that efficiency goes down as the temperature of the air approaches the temperature of your engine. Try a google or wilkipedia search on Carnot (pronounced with a silent 't') and you'll find more details.

cheers

Answer 7

Yes.

Cold air is dryer and denser than hot air. This affects you in two ways:

1. Wet air doesn't burn as well as dry air. After all, there's water in the air.

2. The horsepower of the car is directly related to how much oxygen you can force through the system. This is why supercharged and turbocharged cars are faster -- because they force more air through the system.

The difference can be significant.

On the flip side, you lose milage in the winter if you drive on wet or slippery roads, so it can even out somewhat.

Your worst performance will be driving on wet roads on a hot summer day. Your best performance will be dry roads on a crisp, cool winter day.

Answer 8

I drive a diesel too. Diesel fuel is less flammable than gasoline. Just try to set it on fire. Its difficult. So it would not evaporate with heat the way that gas does. If you are using too much fuel, try changing the fuel filter.

Answer 9

Asisde from the other answeres, your car will have better gas mileage than in cold weather. There isn't a dramatic difference between the temps but your engine has to work a little harder in cold weather.

Answer 10

diesel cars usually get more fuel economy, unless theyre turboed or something or have large engines. but 4 cylinder compared to 4 cylinder, gas and diesel, diesels get more economy. and i think it takes more fuel when its cold. turning on a/c also wastes gas, and when its hot out thats when you use it.