13. Optimize your route.
The less distance you drive, the less gas you use. If you have several stops to make, see how you can route your trip to have the minimum number of miles driven. Keep an eye out for traffic jams, however – often you are better off driving more miles (sometimes even several dozens of miles) than sitting in traffic jams.

14. Consider walking or using a bicycle for short trips,
or use public transportation if convenient and cost effective. Yes, you actually save gas (and money) when you are not using your car.

15. Consider carpooling if possible.
Sure, it's inconvenient sometimes, but it's the single most efficient way to save money on your daily commute.

16. Get a credit card with 5% rebates on gas,
use it for all your fuel purchases and guarantee yourself an automatic 5% savings.

17. Should you use low octane fuel?
Maybe. If your owner's manual calls for premium, use premium. If you use regular instead, the cars computer will retard the ignition timing automatically to prevent detonation. This will have a devastating effect on gas mileage, which will more than offset lower fuel price. Detonation occurs only on full or almost full throttle, so you may be safe using lower grade gasoline in this case if you are conservative with your acceleration habits. It all depends on your driving style and how your car's computer handles the changes. It might be worth giving it a try.

18. Do you need to do a tune-up?
Maybe not. You will never recover the cost of a tune-up in fuel savings. However, you should do regular maintenance, not only for gas saving, but also for performance and reliability. Don't go to a garage and buy a tune-up, 10,000 miles before you need it because you think it will help your mileage... it doesn't work that way, sorry.

19. Do you need to switch to synthetic oil?
Maybe. Synthetic oil is great for engines, and does help gas saving a bit, by decreasing parasitic losses in the engine. But it is significantly more expensive than the regular oil, and its gas saving effect is nowhere near a trade off for its price. However, if you are already considering a switch to synthetic oil for any reason, you can surely also count on some gas savings as well.

20. Do you need to quit using A/C?
Not really. If you drive at highway speeds with your windows open, aerodynamic drag will consume more gas than A/C. At lower speeds you may want to open your windows and turn the compressor off, at higher speeds, use the A/C. It's time to close the windows at 50-55 mph for most cars.

21. Should you avoid excessive idling?
Yes, but that doesn't mean you should turn off your car at a red light or when coasting in neutral. Such solutions are unsafe, and you'll consume more gas when you start your engine back up. But do try to avoid parking or idling for any prolonged period with your engine on. Remember that your engine gives you 0 MPG when idling, so when it's running it's costing you money. On the other hand, remember that starting your engine consumes the same amount of fuel as idling for a minute or so and it also puts an extra strain on your battery, starter, and ignition switch, reducing their life and leading to their premature replacement - which will surely cost you money. You just need to apply common sense here.

22. Do you need to use cruise control?
Speed control works best on straight roads. If the road you're on has hills, you lose. Experienced drivers will disengage the control, accelerate down the hill and decelerate up the hill. Cruise control will try to maintain the speed, loosing inertia down the hill and guzzling gas up the hill.

23. Should you stop warming up your car on cold mornings and start driving right away?
It depends... a warm up consumes an enormous amount of gas. You won't hurt the vehicle by driving right away... but you will be cold till the heat is working. So this is sort of a climate dependent answer, if you're in Alaska, and the temperature is -20F *inside* your car, by all means let it warm up first.

24. Do you need to shop around for better gas prices?
Sure, just don't overdo this and burn 5 gallons of gas while you search for a better price. The price difference is probably not going to be more than a few cents, so keep this in mind and use your common sense. Use your phone or the Internet instead of driving to every gas station around. Mapquest recently started "Find Gas Prices" service.

25. Do you need to use a fuel injector cleaner?
Maybe... it is definitely beneficial to your engine's well being as well as gas mileage to have your injectors clean. Just don't overdo this and add a bottle of cleaner to every tank of fuel. Do that and you pay more for the cleaner than you can possibly save on fuel, and you are cleaning something that is not dirty enough to require cleaning in the first place. A reasonable mileage interval is 10,000 to 15,000 for injector additives.

26. Should you drive in a higher gear?
Sort of... especially in a standard shift, you want to drive in the highest possible gear, without overloading your engine. Generally an engine is most efficient around the middle of its RPM range. More specifically - slightly lower than the torque peak RPM's. If you are in too high a gear your engine RPM'S will "lug" or drag down the engine. Keeping an engine speed too low (closer to idle) will overload the engine, increasing its wear and seriously hurting gas mileage. Automatics do the thinking for you, but with manual you have to develop this skill for yourself.

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.