Towing with the A/C on

For quite awhile, I've resisted putting on the air conditioner as soon as it gets a little warm, whereas Ellen puts it on immediately.  My theory has always been that I would rather have the windows open, so that I don't lower my gas mileage until it gets too uncomfortable.  Then, I will turn on the A/C and not worry about it.

Well, I just read an article or two that said in reality, the increased wind resistance you get when you open the windows and drive is actually more of a drain on your speed and gas mileage than the A/C, because with the A/C on and your windows closed, you have less wind resistance.  Assuming that's true, do you think it applies when towing?  In other words, should I just turn on the A/C when towing in warm weather, and when I do, what impact will that have?

[Civil_War_Buff]

Interesting topic.  I have always "pained" when tow and will use the A/C sparingly.  I keep an eye on the engine temp, and if it starts to rise I will turn the A/C off, but if it's warm, I will turn it on!!  

I think that as far as the windows dilemma, I think it does affect mileage to drive with the windows open, so I try to avoid that if at all possible.

I am sure everyone has a opinion about this, but as for me, I let the temp gauge be my guide.

Larry

It's been well documented for some years now that using the a/c instead of having windows open is better for fuel economy and overall performance.

I usually will turn off the a/c when pulling a hill for example, so that I don't rob the powertrain of any additional power, and add to the heat load any more than necessary.

Just a thought.

Gregg

I might be of some help here as I drive on average between 100-140 miles a day 5 days a week in my own personal vehicle which doubles as my tow vehicle in my job. I drive a 1991 GMC Jimmy (same as an s-10 blazer) with a 4.3L engine, 2 door. I would have to say it depends on the vehicle actually. I notice a *significant* difference in mileage when I drive with my AC on from when I'm just running with my two windows down. On average, I have to put $20.00 worth of gas every two days, (paid for by my work). Yes, gas prices affect a lot, but over time I've learned at least with my TV, I get a lot better mileage by running with my windows down than while using my AC. (I turn my trip odometer over every time I put in that $20.00 worth of gas and keep a pretty close eye on it). Basically, I get, (give or take a mile or two), about 17 miles to a gallon, if I run my AC, I get about 13 miles to a gallon. But again, that's just my personal TV, another vehicle it may vary greatly. Why so? A reason not *anyone* in here has probably thought about! The size/thickness/and number of tubes, basically the cooling capacity of their a/c condenser! As we mainly sell only 3 products: automotive radiators, condensers, and a few gas tanks, we're specialized and I'm very familiar with how they work. Basically, there are a few companies out there we will not deal with on condensers because their aftermarket ones just don't cool efficiently, thus causing the compressor to run, and more strain on the overall system and engine as they are too thin, too short, too narrow, etc.....which basically means they don't cool very good. They fit yes, but they just can't hold the cooling capacity a better brand might offer. Anyone in this group ever had their front end repaired after a car wreck and their AC doesn't seem to cool as much as it used to before the wreck? Have it checked, and it *is* holding a full charge, but still doesn't seem to cool like it used to, well that's why! Your crash shop saved some money on the estimate by going aftermarket, and bought the cheapest thing they could find.........Your insurance paid full original equipment price, yet bought an aftermarket condenser which cost the crash shop 2-3 times less than the original equipment one! (Well, depending, we get 5-10 calls a day from insurance adjusters ourselves). The condensers we carry are either Performance Brand, or Visteon......Both meet or exceed Original Equipment, (OE) specs. Visteon in fact are who builds all of Fords radiators, condensers, evaperator cores, etc. (Basically, they *are* the OE manufacturer for Ford, Mazda, Saturn, etc etc......) And as far as other vehicles, they meet or exceed the other vehicle's specs. Our company was the very first on the whole east coast to do what we do, been doing it for 17 years, now there are places *everywhere* doing what we do, and a lot of them have failed because they sell that cheap junk. But basically, bottom line, condensers do for your a/c system what your radiator does for the engine, absorbs heat. Different vehicles have different sized condensers, they vary in both thickness as well as the design. Bottom line, one would have to do exactly what Texas Camper suggested to find out what a difference it makes with their particular tow vehicle, but at least ya know why now!

[glow=red,2,300]Happytrails.............[/glow]

We have towed our TM across county (over 16,000 miles) and our 28' Tahoe across county (over 15,000 miles), across the Rockies several times, into the Sierras many times, through the northwest and the southwest.  We NEVER hesitate to turn on the A/C when we begin to feel uncomfortable.  In our opinions (dear wife included), it is better to arrive at your destination comfortable and rested... that's why we have the A/C option in our tow vehicle.  I can honestly say that none of our tow vehicles in the past 10 years has overheated because we had the A/C on while towing in the mountains.  If you keep the vehicle properly maintained you shouldn't have any problems with overheating.

Excellent feedback, folks.  (and good info about condensers in case any of us has an accident).  As Gregg notes, I always turn off the A/C going up really steep grades, because I want all the power to pull up the vehicle.  Like Larry, I have used the temp gauge as an ultimate guide, but have just been stingy on the A/C.  This has frustrated Ellen no end, because she usually rides in the third seat of the tow vehicle so she can see to the needs of our kids better.  

I will tell her of these results and she will be very happy!

 I wouldn't worry about the drain on the engine or towing capacity too much. My tow vehicle - and I imagine many others have this feature - shuts off the compressor when the engine is straining up a steep grade. It starts up again as soon as we crest the hill and I let up on the accelerator pedal.
 Check it for yourself by pushing the pedal almost to the floor when going up a grade. You should be able to hear the compressor disengage and feel the air flow warm up a bit.

Bruce

I pretty much agree with everything that's been said so far, but I thought I would summarize a few thoughts.

Modern cars are designed to be fuel efficient at cruising speeds, with windows closed and A/C on.  Around town at lower speeds (where aerodynamics is not a factor) you'll probably get better fuel economy with the a/c off.  However, it varies by model and torque of the engine.  All the stop and go is what kills you, because the compressor is fighting you all the way up to cruising speed...  Ironically, I want a/c even more in the city versus the highway.

Almost all cars are equipped with a/c cutouts to give vehicles maximum power at full throttle.  On the other hand I don't always mash it to the floor going up hills, so I occasionally use human override and switch it off if I need a teency bit more ooompf.

Each car is a little different, but most are equipped with sophisticated sensors to keep things as efficient a possible.  Even though most of the time (especially in the south) we don't complain about the extra $ to run the a/c.