fuel economy observation with and without A/C
07-20-2006, 07:51 AM
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fuel economy observation with and without A/C
it's been stupid hot in MA (and a lot of places), so driving home from work last week and early this week i've been cranking the AC. most of my commute is backroads, where i'm going like 40mph, and staying in 4th gear for 10 to 15 miles. with the AC on, i've been getting like 29-30 miles/gallon ('02 TQM, no engine mods, 93 octane all the time).
yesterday it was actually really nice while driving home (low 80's, and not really humid), so i turned off the AC and dropped all the windows. i was getting over 33 miles/gallon (peaked about 33.6) on the same roads, going about the same speed.
i don't know how accurate the mpg computer is in terms of absolute economy, but i'd be willing to guess that the the variation from trip to trip will be fairly stable. (yes, i'm an engineer).
has anyone else seen this much of a change with and without the AC on? it might be normal, i've just never really noticed it before.
yesterday it was actually really nice while driving home (low 80's, and not really humid), so i turned off the AC and dropped all the windows. i was getting over 33 miles/gallon (peaked about 33.6) on the same roads, going about the same speed.
i don't know how accurate the mpg computer is in terms of absolute economy, but i'd be willing to guess that the the variation from trip to trip will be fairly stable. (yes, i'm an engineer).
has anyone else seen this much of a change with and without the AC on? it might be normal, i've just never really noticed it before.
07-20-2006, 08:16 AM
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Sound normal to me too.
Plus the change in weather can effect your numbers.
Different temp, air density, humidity all probably effect the engine.
Higher temps alone could make your tires more sticky and reduce your mileage.
(Yes, I'm an engineer too...lol)
Different temp, air density, humidity all probably effect the engine.
Higher temps alone could make your tires more sticky and reduce your mileage.
(Yes, I'm an engineer too...lol)
07-20-2006, 08:41 AM
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there must be something wrong....
OK, if he is getting that kind of mpg and I'm not even close then my car is messed up. I do mustly city driving and I understand that is where you get the worse fuel efficiency, but I never get more than 22mpg. Most of the time it's less!
07-20-2006, 09:23 AM
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maybe not...
because i also do a lot of city driving, and in the city i only get like 15mpg. it's just a big fat car to get up moving, so having to stop and go and stop and go is going to destroy your average.
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07-20-2006, 10:32 AM
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but when the windows are down isn't there more friction :)
It does sound right though for sure. I drive with my windows down a lot, but I still leave my A/C on speed 1 ... so it's probably pretty inefficient to do that 
