Surprise: Using car's air conditioning saves gas

I have a buddy who put a 2.2 liter 911 engine in one. I also know of someone who put a 3.2 liter 911 engine in one. I hear it's really funny to see the looks on the faces of drivers that you pass while driving a Bus--going uphill. While towing a trailer...

-soD

 

Part of the secret is turning temp up on AC so it doesn't kick on any more than needed. I had ceramic tint put on my car which helps a lot with heat rejection. Especially with black seats, and no, I didn't have a choice of interior colors or I would have chosen white.

 

It is Hot and Humid in NOLA- 8 months a year.March thru Oct.
I ran the AC all the time because my wife would have killed me if I didn't.
Now I will try to run it when I am coasting down a bridge
or coasting to a redlight
But in general if it is hot enough to make me sweat-the AC goes on.

The Suburban is white-good thing-but the Prius is black with black interior-terrible in NOLA(good price on it in 2006-I would never buy black if it wasn't a great deal)

 

Depends on the car. Even on the freeway where ac should hold it's advantage, my best ever was 43mpg vs damn near 51 without, normally closer to 45-47. I have come to the conclusion though that my ac is just a really inefficient one. In-town I usually get at least mid-30s but my best with ac is 28. Manifold gauges and such confirm it is charged and running normally.

 

Let's see if this image works. I took some readings with my Prius using a scangauge. Now keep in mind, this is low speed, short distance. The OP is about long highway trips which are completely different (for one thing, once the A/C gets the car cool, it won't work as hard, but I didn't drive it that far, so for me it was worst-case).

 

I haven't done any controlled tests with A/C in my Prius , but my seat-of-pants testing says fuel efficiency in city/suburban driving takes a big hit. Maybe even 15%. I don't require it and use it very rarely.

 

Years ago I did a mini-experiment with my 98 GMC K1500. For one week, I drove with the windows up, and the a/c off, no matter how hot it got. The next week, I drove with the a/c on max, all the time, no matter what the outside temperature was. The difference in mileage was less than 1 MPG - pretty much statistically insignificant.

In the FEH, it is hard to say, since the a/c will come on automatically if the pack gets too hot. That being said, if using the a/c on its maximum settings, it does not let the vehicle enter electric mode.

 

IMHO, .8 mpg loss on 16 mpg (5%) is statistically significant particularly when A/C demand is so amazingly small for a K1500 compared to a smaller car.

 

5% is pretty good compared to the 10% on the freeway and 1/4-to-1/3 hit the Echo takes in the city. 5% would be enough to just offset the summertime heat gains and keep a pretty constant MPG all year, so I'd take that number all day long!