Air Conditioner Effect on MPG (tested at 65 MPH)

[R01k]

I've seen that the A/C takes 2-4 mpg. Has anyone noticed the same or are my observations exaggerated?

---

Admin note: see Yttrium's A/C testing results in post #28.

[Daox]

That sounds about right. Some studies have said A/C can drop your mileage 10%.

[Ares]

Even more, I think, on cars with low HP.

There was another thread on here where someone stated he feels a 'drag' during cruise control. I believe I mentioned it to be the AC kicking in/out.

[DonHoot]

I haven't tried to shut it off on my car yet. I always use the "auto" setting on the climate control. If you check out my Fuel Economy Log you can see the results of AC always on.

As a postscript ; It's 90 degrees and humid here I'm not shutting it off to find out the effects of no AC on mpg.(Sorry) !

[Ares]

Lmao. Try living in Houston. I lived with a vehicle without AC for 4 years or so.

[Charlie]

Actually, I can DEFINITELY tell a difference between AC and no AC. I have actually noticed less throttle response when the AC compressor activates. And actually, when I go onto an onramp to merge into highway traffic, I make it a point to turn off the AC during my acceleration phase and when I've successfully merged into traffic flow and reach cruising speed of 65 mph, I'll go ahead and turn the AC back on. Then again, I'm highly obssessive over the smallest of details so I can admit that this is probably over the top lol. I have a CVT transmission if this makes any difference to anybody. It is no mere coincidence however, that I've been able to reach 58 MPG on my way back from work (nighttime) where I don't need the AC and keep the windows up.

-Charlie-

[M-88]

Most vehicles will kick off the compressor if you have your foot in it enough.

On my Focus, it takes 4-5 MPG on the highway to run the A/C.

My Jeep, don't notice any difference, to be honest. 19MPG on the highway nomatter what you do.

[Charlie]

Most vehicles will kick off the compressor if you have your foot in it enough.

On my Focus, it takes 4-5 MPG on the highway to run the A/C.

My Jeep, don't notice any difference, to be honest. 19MPG on the highway nomatter what you do.

That makes sense, but for me I definitely never have my foot heavy on the gas (never flooring it), even accelerating on the onramp. Always seeking that smooth, more gradual acceleration for best mpg possible so I'd never be able to kick off the compressor using that method. Good to know though!

-Charlie-

[91cavgt]

Several years ago, a friend dynoed his 1997 Chevy Cavalier, and he forgot to turn off his A/C. So on the next pull, he turned the A/C off. His car did not automatically turn the compressor off when he went full throttle. What we found is the compressor took 7 hp to run it. 7 hp might not sound like a whole lot if you are at full throttle, but at lower rpms where it might only take 20 hp to maintain speed, 7 hp is a lot of power.

[Ares]

Some vehicles turn it off at a certain RPM - I think Hondas do at 5k.