How much does your ac affect your mileage?

[craveman85]

I haven't updated my vehicle mpg here in a long time but I keep track of it vigilantly at home. My 2008 ranger 2.3 5 speed rwd averages 27.6 over it's lifetime. Upper 20s low 30s in warm weather and 24+ tanks in the winter. My biggest killer seems to be the AC in the summer though. I try not to use it but I've always had an issue with heat. I wear shorts and t shirts year round even below freezing. But anything above 75 is uncomfortable and anything above 90 is almost crippling to me. I only use my ac when it's above 83ish but it hacks about 6mpg off my trip home from works average. Is a 20% loss common? I had my ac checked/serviced last year but they said nothing was wrong with it. Seems like it really kills power in my little truck too. What % loss is your ac in your vehicles?

[Ecky]

Before my engine swap, 25% was a realistic loss in fuel economy, but I don't have a baseline with the new larger engine. Running the compressor adds close to a fixed amount of fuel consumption so the less fuel you're using overall, the larger the percent loss in economy.

[slowmover]

Open windows create drag.

Those windows open also increase fatigue via wind noise, dust, pollen, vehicle exhaust, etc, being pumped thru the vehicle.

Being fresh and alert at the end of the trip counts for more than some tenths. Against the ANNUAL average mpg, what’s the penalty? 3/100’s of a cent?

HOW you use the vehicle will always come first. And I doubt anyone has dead-lowest usage charted except for a minimal period.

A car is about convenience. Designing one’s life so that ownership is NECESSARY is the problem.

What (in your use) would some further discipline gain in terms of fewer engine starts? (No one thinks twice about turning a light switch on or off. The car is a whole different set of penalties to turn on per convenience. You aren’t walking thru your home with a flashlight to avoid engaging the main, are you?).

Track the number of engine starts per per week. Isolate the cold ones (after four hours). And get Average MPH to a higher number.

A/C is a great tool. Keeps one from having to change clothes at each destination. Etc.

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[teoman]

Audi A3 2012 1.6 tdi.

Shows AC consumption.

Depending on how hot it is outside. It is consuming between 0.3 to 0.7 liters of diesel per hour.

Per hour in my opinion is the correct way to measure it. Then your equations for travel might favor a very slightly higher speed.

[jcp123]

20% doesn’t seem out of order, really.

I believe that a/c drag increases more slowly than engine output as you go from smaller to larger vehicles, so smaller vehicles tend to take more of a hit than larger ones. My Echo and Civic both take pretty big hits, similar to yours, where my wife’s Town + Country, at roughly 2.5x the displacement, interior volume, and engine output, barely even registers a drain, probably on the order of under 10% (I don’t drive it enough to really know). Granted, it’s nearly two decades newer, so that probably helps vs my Japanese beaters.

[teoman]

Using percentages of mpg is wrong in my opinion.

Galons / hour would be a more appropriate measure.

[slowmover]

Originally Posted by teoman

Using percentages of mpg is wrong in my opinion.

Galons / hour would be a more appropriate measure.

Liters per 100-Kilometers covers a wider span of use. With boats and airplanes, I’d agree about Time having precedence.

Sorry, though, this is the USA. We should have converted to metric in 1903. Rationality wasn’t part of that false resistance to a needed change. Efficiency & Clarity don’t impress us.

In the meantime, noting a fuel burn penalty as a percentage is partly dependent on knowing what is possible for that vehicle (and conditions). Being off from previous by 19% usually means a vehicle problem.

But, just getting others to record annual gallons is heroic.

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[craveman85]

I checked my gallons per hour at idle and speed with closed windows, open windows, and closed with ac on. At idle the AC kicked it up .25 gph. At 35 it was about .27. And when I checked at 65 it looked about .3

[craveman85]

Seems to increase even more on hills. Maybe because my truck doesn't have much power as it is and it's giving it up for the ac

[craveman85]

Oh and windows down showed almost no effects on my gph