There are few things whose knowledge alone is very useful & helpful in our day-to-day life. This section is a collection of such knowledgeable articles. Do not miss this one.
27. Do you need to slow down to 55 mph to save fuel?
Not really... every vehicle has its most efficient speed in the highest gear. It differs depending on the design of the car, and things like tire pressure, open windows, bike racks, etc. The 55 mph speed limits come from the 1970s, when a nationwide speed limit was established in an attempt to reduce gas consumption at the time of an energy crisis. This attempt failed miserably by the way, but that's another story. Which does not mean speed does not matter... it does. For modern aerodynamically enhanced cars, the most efficient average speed is more in the range of 65 mph or even higher. You don't want to exceed that speed if you are trying to maximize gas mileage. At higher speeds, the main gas eater is aerodynamic drag, which is proportional to the square of your speed. That means your car needs four times more fuel to overcome the drag when you double your speed.

28. Do you need to buy a more fuel efficient car.
Sure you do! But it is probably not a good idea to dump your gas guzzler below market so you can replace it with a new Corolla. If you are shopping for a new vehicle however, considering a more fuel efficient model will definitely help.

29. Do you need to replace your air filter?
No... because on modern cars, computers compensate for clogged air filters. You lose performance if your filter is clogged, but your gas mileage stays the same.

30. Do you need to replace the fuel filter?
No... if anything, a clogged fuel filter will improve your mileage on older cars. On newer cars, the computer will compensate for most filter issues. On the other hand, if your fuel filter is clogged to the point where your engine starts starving for fuel at full throttle, then you will see... and feel... a serious loss of performance, well before it will affect your gas mileage in any way.