Car and Driver looks at mileage myths and misconceptions

In the latest issue of Car and Driver my friend Mike Austin has taken a look at a variety of different beliefs that people have about what saves fuel when driving. As we all know by now, driver behavior does have a major impact on fuel consumption. Mike and his test colleagues went out and ran mileage tests evaluating factors like using air conditioning vs. having the windows down vs. the sunroof open, removing extra stuff from the trunk, and running with stuff tied to the roof. The A/C vs. windows test yielded some interesting results. Only one car was tested in this case. A test with a variety of cars may have turned out differently depending on the aerodynamic properties and how air flows around the car.
They also talked to some engineers about the effects of putting the transmission in neutral while coasting and of course shutting off the engine while the car is stopped. That last one is not generally recommended for cars that aren't designed with auto start/stop systems. It puts a lot of extra wear and tear on the starter and lubrication system as well as causing other potential problems. Its also very inconvenient if, like most Americans, you drive an automatic transmission car. At a drive through, for example, you'd probably be better off just parking and walking inside to get your fast food fix. Check out all of Mike's results and, as always, remember that your mileage may vary.

[Source: Car and Driver]