im probably all late on this one but yeah it doesnt make that much of a difference. it's better to have ur ac on rather than keeping ur windows down jsut cuz u dont wanna waste gas. i used to think that but i found out that if u have ur windows down while ur driving ur using more gas. it's pretty much self explanatory. having ur windows down is just pushing the car back. does that make sense lol. i duno how to explain it. im a noob too.

 

I just got my Civic DX (used with 86K miles) and the first fill-up I got about 37mpg... and that was with the A/C everyday driving to work and home. I just filled up again today and haven't used my A/C as much over the last week or so and I'm still getting 37mpg... and this is with a O2 sensor CEL.[8D]

It seems like having the A/C is doesn't have a significant effect on my mpg with the Civic DX. Now if I used my Evo and have the A/C on everyday, during the week... that would have been another story.

 

unless your ac compressor is all out of wack, just don't worry about it.

 

ya AC doesnt hurt the milage to bad.... but it will lower it...... i typicaly get about 2mpg less... and with my stereo system my alternator is working just as bard so ive lost about another 1-2mpg.... BUT having COLD AC and a bumpen stereo its no concern to me!!!!!
still beats the crap outta my trucks old typical 15mpg! civics running a average of 28-29mpg when i got my civic i was geting ruffly 33mpg stock and 38mpg all highway... last highway trip i got only like 34mpg..... but like i said STILL awhole lot beter than my truck.LOL

 

On a different note, ac does affect your power. I notice a huge difference in accelleration at red lights, or on on ramps when the ac is on, so i usualy turn it off if i need to speed up in a hurry, and click it back on a few miles down the road when it's had time to rest for a sec.

I notice a little bit less mileage as well, but when its 100* you really don't give a crap.

 

o ya dito with the take off accelerating.LOL

 

I didnt read all of the posts, but your A/C does use a LITTLE bit more of gas, but nothing to be up in the air about, you will actually waste more gas by keeping your windows open because of the drag your car creates. You should shut off your a/c and open your windows when you are stuck in traffic or moving slow, thats when its worth it if your worried about paying a buck more at the pump.

 

Trust me - when you have an aging VTEC-E, you notice the performance loss and mileage decrease when the A/C button is lit. The compressor steals like 10 horsepower from the engine in parasitic drag. My hatchback can barely get out of its own way until I'm rolling at least 15 mph.

So I usually just turn off the A/C until I'm moving along nicely, then I'll turn it back on.

I'm going to have a 'turbo' decal made for the A/C button... and stick it on in plain view.