Here are a few big myths:
1)It takes more fuel to start a vehicle than it does to let it idle.
People are really confused about this one and will leave a car idling for half an hour rather than turn it off and restart. Some kids I know started an anti-idling campaign in the suburbs and are shaming parents into shutting down their cars.
Idling uses a quarter- to a half-gallon of fuel in an hour (costing you one to two cents a minute). Unless you're stalled in traffic, turn off the car when stopped for more a few minutes.
2)Vehicles need to be warmed up before they're driven.
Pshaw. That is a long-outdated notion. Today's cars are fine being driven off seconds after they're started.
3) As a vehicle ages, its fuel economy decreases significantly.
Not true. As long as it's maintained, a 10- or 15-year-old car should have like-new mileage. The key thing is
maintenance -- an out-of-tune car will definitely start to decline mileage-wise.
4) Replacing your air filter helps your car run efficiently.
Another outdated claim, going back to the pre-1976 carburetor days. Modern fuel-injection engines don't get economy benefits from a clean air filter.
5) After-market additives and devices can dramatically improve your fuel economy.
There's not much evidence that these "miracle products" do much more than drain your wallet. There are no top-secret 100-mpg add-ons out there.
6)Using premium fuel improves fuel economy.
You might as well write a check to BP if you believe this. Only use premium if your car specifies it.
Read more here: http://fueleconomy.gov/feg/topten.jsp