i was told that if your going over 35 mph you should close your windows and use the fan instead (to save gas), due to wind-drag.

an open sunroof doesn't seem like it would create as much wind resistance as the side windows being open, but i'm not certain.

basically, i'm wondering that if keep my sunroof open, should this impact my mileage as much as keeping the side windows open. dunno.gif

 

The difference is so scant, especially with a sunroof, it's not really worth it.
Work out the math on it too - IF you got a 1mpg increase (that's a big if, I suspect it wouldn't even be close to that), that's only a 3.3% increase in mileage, and 3.3% off a tank of gas is $1 at the most.
Worth it? That's up to you.

 

on a 10 gallon fill-up at $2.50 a tank is $25. 3.3% is $0.83. Say it's a dollar. Say it's $2. How much do you like having your sunroof open?

You run a full tank with the roof open, another with the roof closed. Repeat the test a few times if you're OCD. If there's a notable difference in your MPG, the difference is what it's costing you . . . is it worth that much to you to run with the roof open? Then don't sweat it.

 

Mythbusters did this. I think they determined there were no noticeable differences between running the A/C and having the windows down.

I think I feel more response when the fan (not A/C) is on and windows are down with sunroof open. Maybe the air just flows better and isn't hitting a wall with the fan closed.

Do what you want, it won't affect gas mileage.

 

http://en.wikipedia.org/wiki/MythBusters_(...s._Windows_Down
Tests were performed under varying conditions (55 miles per hour (89 km/h) versus 45 miles per hour (72 km/h)). Also, the 55 mph test was using a computer to estimate fuel efficiency based on air intake, not actual fuel consumption, and showed A/C was more efficient. The 45 mph test consisted of running the tank until it was empty, and showed open windows were more efficient. This experiment—or one like it—is sometimes cited by the Magliozzi Brothers on Car Talk when presented with this question.


http://green.autoblog.com/2007/08/29/mythb...s-down-episode/
They got an SUV and attached a sensor that estimates mileage by measuring air flow to the engine. They did 15 laps around a track, with a constant speed of 45 MPH, measuring mileage as they went. They did 5 laps with the AC off and windows down. 5 laps with AC off and windows up. 5 laps with the AC on and windows up. No laps for AC on and windows down. Here are the results.

1.AC off, windows up = 11.7 MPG
2.AC off, windows down = 11.3 MPG
3.AC on, windows up = 11.7 MPG
So, according to these tests, AC use does not impact mileage. Windows down hurts mileage about 5 percent. The better option is turn on your AC. Rolling down your window makes little difference at all. Apparently unsatisfied, they tried a totally new test, measuring mileage differently and even changed the variable of speed. This is important for the revisit which showed speed was very important. How they did second test is after the jump.

 

these gas mileage threads are retarded

you guys drive 4/6 cylinders

99% of us get better than 20MPG and if your not...your either boosted to no end, or got a shitty running car

 

+1 but some people really really care, AFTER they buy their car. For them, there are a few adjustments they can make to the nut behind the steering wheel, which will affect gas mileage.

The best gain I ever saw was 35%, from not driving in the city in traffic any more. Next best gain was +15% from doing the auto --> manual conversion.

 

I'm seeing ~15% increase driving my auto just by using the manual shifting feature

 

best mileage i got was (and i may be off by a few miles) was 38mpg

i was traveling 200 miles on the freeway...............@30-35mph

i blew 3rd, 4th, and 5th gear on the way back from seeing my at the time girlfriend limped it home cuz i couldnt afford a tow

 

I got 31mpg once in my tib, interstate following my parents so I was on cruise control the entire 170mile trip

Every other time it was a steady 20-21.