This is not another "bad mileage" thread first off. What I have noticed (and I might be crazy) but I get better mileage with the A/C on and that makes no sense except that the engine heats up 10 times faster with it on from being cold. Think that has anything to do with it? I do know that the less times you cut the car on a off you definantly get better mileage. Just some observations of mine, what do you guys think or have noticed?

well, some schools of thought seem to think that cars get better gas mileage with the windows up and the ac on because even though there is extra load from the ac, it still has less of an impact than the increased drag from having the windows down. this is especially true at highway speeds.

my car in college was a 97 sentra. and it even recommended in the manual running the ac when highway driving for that reason.

and since you live in NC, you are in the same boat I am...hot, humid hell. i've had my car for 2.5 months, and have been using the a/c 100% of the time for 2 of those months. and i'm averaging almost 19mpg, with daily 9k runs.

well i normally get 17.3-17.4 mpg (85% city )..with a/c on i get about 17.2 mpg...so it doesnt' really effect me one way or the other. no flooring it around town with a/c is anouther story (well flooring it in general)..hehe

aaaaaaaaaaaaaaaaaaaarrrrrrrrrrrrrrrrrggggggggggggg gggggggggggg!

AC on + windows up = no rotary music = boooooo...;)

Actually here's something I've been wondering about...if you turn your fan on but not the AC, wouldn't the fan actually help as an intake of sorts to pull in air?

^^^ yup...into the cabin. :p

the air intake for the a/c is completely independant from the air intake from the car...i believe the air intake for the a/c is at the base of the windshield, but i'm not positiive of that.

although, one thing i've noticed is if you have the a/c turned off (fan set at 0) and the mode set to fresh air, air will blow through the vents anyways, especially on the highway. this is the first car i've had that does that.

I have noticed no difference at all in gas mileage when using A/C and when not using it. Which is a really nice feature of this car...

and it even recommended in the manual running the ac when highway driving for that reason.



the Manual of the RX-8 does also.

From my experience there are 4 things that make a difference in your gas mileage, and they all have a much greater impact than AC:

1) How quickly you accelerate.

2) Your cruising speed.

3) The octane of gas that you use (lower octane = better mileage).

4) The wind.

In other words, don't worry about how AC affects your mileage.

Just something that I had noticed, seemed weird but I guess could be contributed that with the A/C on I probably accelerate less quickly so that might have something to do with it.

I average 18-19 MPG (Hywy/City combined), whether I drive fast, slow, AC, No AC...It never seems too change. Sometimes I'll get 17, but that's when I am at highway speeds and I keep winding out 3rd & 4th gear just for fun (basically burning gas for no apparent reason cruising in the 7K RPM range :D ).

3) The octane of gas that you use (lower octane = better mileage).
I went from 93 to 87 for a couple of weeks and lost 15% in gas mileage.

--Massive

The show 'Mythbusters' actually tested this once. If i remember right, the car with the A/C on did get slightly better mileage. But i think that the difference was very small. So i'd say drive with whatever makes you happier. Personally i like the windows down.

one thing is certain: this car likes hot weather !! We are in the midst of a heat wave up here in MTL with 90F and high humidity and my gas mileage is at it's best. Comes fall... it "falls" down as well.

The show 'Mythbusters' actually tested this once. If i remember right, the car with the A/C on did get slightly better mileage. But i think that the difference was very small. So i'd say drive with whatever makes you happier. Personally i like the windows down.


yup, but they tested it at ~45mph. at higher speeds, it makes a larger difference, so if they had taken their exploders up to normal highway speeds, then the difference would have most likely been larger.

i like windows down too, but its way too hot and humid for that now. windows are staying up and a/c on until mid-september most likely.

one thing is certain: this car likes hot weather !! We are in the midst of a heat wave up here in MTL with 90F and high humidity and my gas mileage is at it's best. Comes fall... it "falls" down as well.


I've noticed this too, strange as it is. For an engine that runs crazy hot you'd think it'd prefer a little cooler weather. :confused:

i think that is from the winter blends that colder climates get. apparently (never used the stuff, it stays warm enough down here) its not a very effecient fuel.

I also get better gas mileage with the A/C on too!!!!! This is not physically possible, but this is also what I am noticing?????

The only explanation I can think of is the summer gas formulation is better suited for the RX-8. The refineries add less butane, propane into the gasoline in the summer than the winter. This is all based on the RVP (Reid Vapor pressure) formulation needed for summer (less vapor pressure) and winter (more vapor pressure) driving.

I also get better gas mileage with the A/C on too!!!!! This is not physically possible, but this is also what I am noticing?????

sure it is. the parasitic drag on the engine from the a/c increases the engine load less than aerodynamic drag from windows down driving does.

does driving with the A/C on impact the performance of the car? That's my only question.

slightly...although unless you are at the drag strip or otherwise racing (legally i hope), you'll never notice.

for all the ecu flashes before P, the a/c cuts off at 5500 rpm, and for the P flash, it is bumped up to 7500 rpm.

slightly...although unless you are at the drag strip or otherwise racing (legally i hope), you'll never notice.

for all the ecu flashes before P, the a/c cuts off at 5500 rpm, and for the P flash, it is bumped up to 7500 rpm.

Now what the heck is the 'P' flash? Last I knew there was 'N' :confused:

Now what the heck is the 'P' flash? Last I knew there was 'N' :confused:
http://www.rx8club.com/showthread.php?t=61058