GenVibe - Community for Pontiac Vibe Enthusiasts

Need some feedback on mileage drop with a/c running. I've had 3-4 mpg drop in mixed driving, which seems excessive and I'm not an aggressive driver.

That's about the difference I'll get using the A/C. This is for the most part normal just due to the higher load the A/C system puts onto the engine due to its already small rating (4-cyl).

Im not sure if it depends on the blower speed and if its just AC or Max AC, but I think I only lost 1-2 mpg when i had AC on low last summer.

If you are in town less than 45 mph, dont use a/c and lower the windows above 45mph i use A/c if needed; and only see a 2-3 drop in mileage.

Quote, originally posted by northvibe »Im not sure if it depends on the blower speed and if its just AC or Max AC, but I think I only lost 1-2 mpg when i had AC on low last summer.This is what I see.

Zionzr2, you must live up north. If I do as you suggest, I'll be reduced to a puddle on the seat....I live in FL.

try with the recirc on aka MAX ac and see what happens. or are you already doing that?

Quote, originally posted by vibrtor »Zionzr2, you must live up north. If I do as you suggest, I'll be reduced to a puddle on the seat....I live in FL. heehehobviously comfort superseeds fuel economy!! I dont follow my advise when the humidity increases..Which dose occur from time to time up here in the north.my point was that not factoring in comfort that windows down below 45 mph is more efficent than up with the a/c on and above 45 mph economy is better with the a/c on and windows up versus windows down...the best economy is windows up and no A/c and minmal use of anything electrical.

I don't normally drive the Vibe, and haven't figured lately. (not sure how often she runs the A/C) I've hardly turned off the A/C in my Maxima the last 2 months, and my mileage hasn't really even budged.

I filled up today and lost about 2-3 MPG. I drove more in town than normal but the a/c has also been on almost all the time.

In general, since 4 cylinder cars do not generate as much torque as larger engines (V6-V8), they will lose a bit more MPG once you turn on the A/C. They simply have to work harder to overcome the power needed by the compressor. This is especially true in city driving.I don't know how you guys in places like Florida put up with the heat and humidity. I flew out to Virginia from Denver last August for a week long training session. Got off the plane and felt like I had just gained 30 pounds! Thought I was going to need to grow gills just to breathe!

have you done the AC insulation mod? that will help get it colder faster and may help?

Thanks for the response from everyone. The a/c mod won't affect mileage, since the compressor is running all the time, until you turn off the a/c (unless Toyota has a design I don't know about). I talked to the local Toyota dealer about the situation and, at first, he said that was a big drop, since the compressor was fairly small and did not load the engine that much. But as the conversation progressed, he backed off, saying he hadn't gotten a lot of feedback regarding the situation. I just talked with the Pontiac dealer and, as I expected, they offered nothing constructive and said to bring it in to have it checked out. Incidently, I had installed a K&N filter which worsened the situation (I also realized NO power benefit) and have since returned it for refund. I'm going up to PA next week, so I'll get a chance to really find out how the a/c affects open road driving. Needless to say, with speed limits in the 70-75 range, I'll be pushing the rpm's beyond the "economical" limits, but it'll give me a good feel for what this car is really about. It'd be nice if the automatic had a 5th gear for open road driving - it'd probably get 40+ mpg.

I check my mileage on every tank and since I've been using my A/C I have not noticed any change in my mileage. The most it's dropped has been 0.3 mpg.

It's been in the 110's out here lately so I usually run the AC near full blast. I've noticed as much as a 6mpg drop.Engine load from the compressor varies and is dependant on ambient temperature and blower speed usage. The AC compressor runs on a thermostat. The hotter it is outside and the higher the blower setting, the more constant the compressor will run. Otherwise it only kicks in and loads the engine every couple of minutes to recool the coils.

You're right. And Toyota verified that (Pontiac, again, didn't know s---). And since it's been so stinkin' hot and humid here lately, and since a lot of my driving has been local with high blower speed, I guess the mileage drop has to be expected. We'll see what happens on the trip next week.

I've heard what northvibe said....use the RE-CIRC option for better gas mileage ya'll, its also better on the engine I hear

I keep track of every drop of gas/mile i put on my car and have experimented quite a bit with AC on/off. In my case it does not make a noticable difference. City/highway driving makes a big difference as well as cruising 75+ vs. 65. The best mileage I have been able to get on my 100 mile/day commute is 37mpg, this is traveling 50 mph. I ran 3 days at each speed to get a good average. BTW 50 is waaaay too slow unless you are riding a bicycle. After checking MPG vs. speed vs windows up/down vs AC on/off I can say the AC made no difference on my car, this also was the outcome when I checked all these factors using the Scangauge.

if you havent done the AC mod DO IT. It will get your AC colder faster and slightly colder over all. The times I do use it in MN its great, so if your in FL it should be a must!

Well, my trip got postponed for at least a month, so in the meantime, I'm gonna insulate the refrigerant line. Anything will help in FL, although since I moved from Ft. Myers to Gainesville, the heat isn't as intense. It's consistently in the 90's, but lower humidity. And it actually cools down at night! We'll see if the mod improves things (both cooling and mileage).