A/C Screws Up MPG

True


iPhone ?

 

There are too many variables there to accuse the climate control system of entirely affecting the results, but yes, use of the A/C, and especially cabin heat, I've found, does reduce fuel economy. Not by half, though. I would imagine other factors are contributing more, such as temperature, traffic, route, actual miles driven, driving style (in a hurry or not?), etc.

 

welcome! that's a better than 50% reduction in miles driven, if he's driving the ams amount each day. i'm guessing your numbers are off, but if not, his car may have a problem. i have nevr seen more than a 20% reduction in the coldest weather, with the heat blasting. a/c uses less than heat, unless you're in a hot climate maybe.

he would do well to start documenting his mpg's at fill up time, and tracking the daily weather.

 

How many miles is he getting out of a tankful? This might be a moot point, if that Prius has a gas tank bladder, in which case it's better to calculate fuel fill up volumes and distance travelled. Summer 2013, I managed over 620 miles out of a full tank of fuel in my Prius II (66.4mpg UK). The A/C was used on its lowest settings at least 33% of the time. We're having a very mild winter in the UK at the moment, so i've got 59.0mpg on my MFD at the moment. I have once seen 48.0mpg during prolonged sub-zero (or lower single digit) temperatures over here.

 

Always have run ours with the climate system on auto or manual and have seen little change in mpg either way.