i was driving today and thinkin about this article i read about someone drove city speeds with the windows up a/c on and got worse mileage than when driving with the a.c off and windows down....similarly, at highway speeds, they got better mileage with the a/c on and windows up rather than a/c off windows down.

i am doing an experiment with three variables, a/c, windows, and then later tailgate....i drive 350 miles a week, with about 40 city and the rest highway. the conditions, route, and speeds are the same for both directions. i will be cruising between 55 and 70 sometimes locked and sometimes unlocked with rpms varying between 1800 and 2500. the rpms will NEVER exceed 3000 and the speed will never exceed 75 to have a few controls. the only thing that should change in the next few weeks that this will be going on is the temperature but not by much so we should be good there. i fill up a new tank of premium every wednesday afternoon.

the tests will be as follows...
this week: driver window down halfway, passenger up, a/c off, tailgate up.
next week: both windows down, a/c off, tailgate up
next next week: both windows up, a/c on, tailgate up.
week after: both windows up, a/c off, tailgate up (its gonna be hot in the cab)
week after: [same as week 2] except tailgate down
week after that: [same as week 3] except tailgate down
if i have time, just to see how bad stuff will get, i will do windows down, a/c on, tailgate down.

note* absolutely no WOT during these tests, no extended periods of time below 55 or above 70. 40miles city driving assumed for all tests. RPM never to exceed 3000.

goal: to determine best set up for highway driving and see how much these variables really affect gas mileage as a whole.




-tell me what you think

 

mythbusters already busted those myths,

 

im not discountin myth busters but i doubt they tested all of these condition real life, real vehicle situations, at least vehicles that we would be driving. im doing it anyways and will post the results i know the tailgate down=better mileage b/c lesss resistance was busted because i know if its up it creates a low pressure bubble that causes the quick air to stream right over hte top, the tailgate thing is just for giggles but wanted to do it in conjunction with everything else

 

yes myth busters did that they took to suburbans i belive and took them around a circle track.....the one with the ac on was the winner!

 

o well, thats what i expected, highway a.c wins, im basically doing this to see how good/bad my mileage can get with these simple changes. right now im seeing like 14ish highway still doing it!

 

and to test the tailgate thing, they took 2 indentical brand new fords f150s and drove one with tailgate up and one down. The one with it up won.

 

I drive 35 miles one way to campus Mon-Thurs every week. My buddy with a 2003 F-150 RCSS 2wd makes the exact same drive.

I've tested this literally dozens of times with the exact same results every time: tailgate down results in 2-4MPG MORE. I always have gotten better MPG with my tailgate down.

My buddy with the Ford has tested this dozens of times too. He always gets the same mileage whether or not the tailgate is up or down.

I've known about the Mythbusters test for quite some time now, but I will tell you; for some reason different trucks respond differently.

 

I think it's a good idea, regardless of what the Mythbusters say. Just cause it worked for them or didnt work doesnt mean it will or wont for you. I say have at it, and let us know what you find out..

 

Strange, according to my instant mpg readout I get worse gas mileage on the hwy with the A/C on and windows up than when I have the A/C off and windows down.
A/C is a killer on my truck, the instant mpg will drop 2-4 mpg as soon as it kicks on.

 

When your AC is on doesn't the computer pull some timing? I think I read that somewhere.