The Mythbusters had a show where they tested fuel mileage with the AC on -vs- Open Windows. They did a terrible job of setting up the experiment. They had two vehicles sitting in different positions. Then "drained" the fuel from the tanks with a hand pump. Then filled the tanks with 5 gal of fuel. Then ran them around the track until they ran out of fuel. The draining process was totally bogus and different drivers are notorious for having different driving habits. Different vehicles don't get the same mileage even if set up exactly the same. They ran the AC full blast also. They need to run that test again. I have seen several badly set up experiments on that show now.

 

how about the show where they did the tailgate up verses tailgate down fuel myth?? that one was a winner also.

 

I think that the AC test should be done with 2 vehicles at the same time, just so the conditions are the same, IE same temp, wind, humidity etc. But with that said what should be done is to actually drain the tanks IE remove them totally and if possible actually put in a clean dry tank then run the test with one vehicle running the AC the other with the windows down, then redo the making sure the tanks are clean and dry and swap vehicles same drivers in the same vehicles but with the oppisite vehicle running the ac.then I think you would have some numbers you can actually use.

 

If the had just set both vehicles on level ground and hooked up power to the fuel pumps and ran the tank out thru an orifice until the back pressure dropped it would have helped. Due to slight changes in the pickup assemblies one truck might have been able to pick up an extra ~gallon of fuel. When running the test if they monitored the fuel rail pressure and stopped the test when it dropped some specific amount it would have made it more even.

They did at least run both vehicles around the track at the same time.

 

yeah but my point is something you noted and that is 2 people driving a vehicle will get different results on fuel economy, and 2 vehicles even setup the same will be different thus my suggestion of flipping them and run the test with the 2 vehicles but with the oppisite setup as to which one is running ac.

 

When Mythbusters gets things right, it's pretty entertaining, but when they get things wrong... well, it's generally still entertaining, but I wish they would make it more clear that their version of "science" is sometimes a little simplistic.

 

I was very close to leaving a message on their web page, criticizing their explorer mileage myth but never got around to it. But yes, the tanks should have been drained properly (or use an auxiliary tank) and both vehicles should have been run under each condition.

 

its not a myth a/c = load on motor = less gas mileage when the car is drove the very
same way without a/c ....have they run out of myths to bust?????????? ...could be
anyone with a calculator,car that has odometer,and runs the numbers can figure out if its a myth ..... I dont care for them much , but I dig the red headed chick for some reason

 

The manufacturers did some real scientific testing a number of years ago and figured out that running the AC was better than running with the windows down. Check and see if you can find any SAE papers on the subject. I think I remember seeing a few.

 

Eric I don't think people understand how that can be true because as 77 put it the AC puts a drag on the engine, yet most people don't realize how much affect wind drag has on fuel economy, and how much little things like rolling your windows down affects aerodynamics

 

woops nevermind...

 

I just did a real quick & crude check on the SAE website and did not see the papers but they are there. If someone has the time they may be able to find them. Unfortunately to actually READ a paper is $$$$$$$$$$$$