Air Conditioner Effect on MPG (tested at 65 MPH)

[Daox]

Considering the Mirage only needs ~15 hp to cruise at 65 mph, 7 hp is gigantic.

Aerodynamic and rolling resistance calculator - EcoModder

[aydu]

Even if you had to stick your foot out of the driver's door and push, I'd still use my A/C.

The Mirage seems to do fine with the A/C running around town and at highway speeds. Probably take a bit of a hit on mpg, but that is the price of comfort.

[Daox]

I agree, there is a price to pay for comfort, and sometimes its absolutely worth it. Not always for me since I live in Wisconsin and it doesn't get crazy hot here, but I do use it (I did just yesterday).

However, you can also use your A/C efficiently too. Here are a few tips:

1) Park in a shaded area if possible, or use those reflective window things.
2) Roll down the windows to initially cool the car off for a minute or two vs just getting in and blasting the A/C on full blast.
3) Always set the temperature control to full cold. Setting it a bit warmer with the temperature adjustment just mixes in warm air which you just spent power to cool down.
4) Use the fan speed to regulate how much cold you want. Once the car cools down, turn the fan speed down versus turning the temperature up. The auto climate control should automatically do this I would imagine. Once the car is cooled down, it won't take nearly as much power to keep it cool.
5) Keep air on the recirculate setting. This takes air from inside the car and cools it versus always taking outside air to cool it.

[R01k]

Here in western New York I can shut it down in some mornings and evenings. Still, I don't really care about losing a few mpg for comfort.

[aydu]

I use the Auto setting on the A/C, set on 70. Seems to do a good job of cooling a hot car without the fan speed blowing you back in your seat.

The A/C in the Mirage is one of the best I've experienced in a vehicle. Cools quickly and to the point where you could use the car's interior as a meat storage compartment - if you wanted to.

[M-88]

Here in western New York I can shut it down in some mornings and evenings. Still, I don't really care about losing a few mpg for comfort.

There's 50 weeks a year I can go without AC in CNY. The problem for me is the hot and ultra-humid days (like tomorrow). My lungs just do NOT work on those days. Then it's a requirement.

[R01k]

There's 50 weeks a year I can go without AC in CNY. The problem for me is the hot and ultra-humid days (like tomorrow). My lungs just do NOT work on those days. Then it's a requirement.

Same here.

[91cavgt]

There's 50 weeks a year I can go without AC in CNY. The problem for me is the hot and ultra-humid days (like tomorrow). My lungs just do NOT work on those days. Then it's a requirement.

In Texas, there are only about 3 months that you don't use the A/C. It is quit common to walk around in short sleeve shirts and shorts in December and January. I have lived here all my life and there are still times that the humidity is so high that I feel like I should be wearing a diving respirator just to walk to my car!!!

[Minihaha]

(Possibly) interesting side note: I could be pulling this out of the air - but I think I recall 'someone' conducting a test (years back) of:

1. highway drive with windows up and AC on
vs.
2. highway drive with windows down and AC off

#1 did better, or they were very close to equal; because the loss of aerodynamic efficiency with the windows down at freeway speeds negated the gain from driving sans AC.
Either way, I am glad to pay for the extra fuel consumption when I 'need' the AC.
Often on a 'warm' day where having the windows open is (IMO) sufficient I will roll them up and turn on the AC during the highway portion (to limit all the wind noise and buffeting) and then turn it back off after the HWY jaunt.

[91cavgt]

(Possibly) interesting side note: I could be pulling this out of the air - but I think I recall 'someone' conducting a test (years back) of:

1. highway drive with windows up and AC on
vs.
2. highway drive with windows down and AC off

#1 did better, or they were very close to equal; because the loss of aerodynamic efficiency with the windows down at freeway speeds negated the gain from driving sans AC.
Either way, I am glad to pay for the extra fuel consumption when I 'need' the AC.
Often on a 'warm' day where having the windows open is (IMO) sufficient I will roll them up and turn on the AC during the highway portion (to limit all the wind noise and buffeting) and then turn it back off after the HWY jaunt.

The TV show MythBusters tested this. On the SUV that they used to test, they found that 45 mph was the break even point. Above 45 mph the SUV used less fuel with the A/C on and windows up, and below 45 mph the SUV used less fuel with the A/C off and windows down.

However, our Mirages have different aerodynamics and different power curves of the engine than the SUV that was tested. With how aerodynamic this car is, I would be willing to guess that the break even point on our cars is at a lower speed. When you drive with windows down at higher speeds, it REALLY messes with aerodynamics typically. Unless of course Mitsubishi designed the car to stay aerodynamic with the windows down (not likely).


The only real way to prove one way or other is to do some real world testing.