You can also check consumer guides, car magazines and Web sites, Web site forums or ask friends, relatives and co-workers which vehicles they recommend as fuel-efficient cars. Don't buy more car than you need, as larger vehicles generally have bigger engines that are less fuel-efficient. Find most fuel-efficient car in size group you're interested in, whether a two-seater, compact, mid-sized, SUV or pickup truck. There are several online sites where you can compare fuel consumption ratings of any car.

Your choice of transmission can also affect fuel efficiency of vehicle. Generally, a car with manual transmission is a more fuel-efficient car than one with automatic-assuming you shift properly. And a manual with overdrive, tachometer or shift indicator is biggest fuel saver, saving up to 10% on fuel costs. If you do buy an automatic, which makes more sense for larger cars, more gears better.

Under normal driving conditions, smaller engines offer better fuel efficiency and economy than larger ones. All other things being equal, larger engine and more cylinders it has, more fuel it consumes. Additionally, cars with smaller engines usually cost less and gas costs are lower because you don't need higher octane gas. That doesn't mean a bigger engine is never a good choice. In some cases, a larger, more powerful engine may provide greater fuel efficiency. If you use your vehicle for work or often tow heavy loads, a smaller engine could burn more fuel if it has to work too hard and function beyond its most fuel-efficient range.

But even if you don't currently own a fuel-efficient car, there are lots of ways you can improve fuel efficiency of your present vehicle until you're ready to purchase one of best gas mileage cars. Your personal driving habits have a big effect on your fuel use and costs. You can better manage your vehicle operating costs as well as minimize emissions it produces by driving less and more efficiently. Here are some tips to help.

First, you need to know what kind of mileage you are getting. Calculate this by filling up your tank and recording odometer reading-or you can reset your trip gauge to zero. Next time you get gas, fill tank again and divide miles you traveled between fill ups by quantity of gas you bought on this fill-up. This is your car's miles per gallon or mpg. If it's pretty dismal, here's how to turn your fuel guzzler into a fuel saver:

Drive slower: The aerodynamic drag on your car increases noticeably faster you drive. The drag force at 70 mph is about double that at 50 mph, so keeping speed down can increase your mileage considerably. Gas mileage decreases rapidly at speeds over 60 mph. Each 5 mph above 60 mph is like paying an additional $.10/gallon for gas. Observing speed limit is also safer for everyone.

Maintain a constant speed: Every time you speed up, you use energy, some of which is wasted when you slow car down again. By maintaining a constant speed, especially driving posted speed limit, you will improve your fuel efficiency. Just by increasing your highway cruising speed from 62 mph to 74 mph you increase fuel consumption by about 20%! Using cruise control on highway helps you maintain a constant speed and will usually save gas.

Drive gently: Aggressive driving-speeding, rapid acceleration and hard braking-wastes gas. These bad habits can lower your gas mileage by 33% at highway speeds and 5% in city. In addition, reasonable driving is safer for you and others, so you may be saving more than gas money. Consider using overdrive gears on highway, as this decreases engine speed, reducing fuel usage and engine wear.

Avoid Excess Idling: Idling gets 0 miles/gallon and wastes fuel and money, is hard on engine and adds to toxic emissions. Cars with larger engines typically waste more gas at idle than those with smaller engines. Turn off your engine if you think you will be stopped for more than 30 seconds. However, if you're driving a fuel-efficient car like a hybrid, your electric motor is on when you idle, so you're not wasting any gas at all!

Minimize air conditioning: Using your air conditioner in hot weather can increase your fuel consumption by more than 20% in city driving. Whenever possible, close all windows and use air vents to circulate air instead of air conditioning. You will improve your fuel efficiency in summer by minimizing use of air conditioning and using your car's flow-through ventilation, especially on highway. If you must use air conditioning, set controls to a level that lets system cycle, and turn it off once interior of car is cooled down enough. Also consider such options a sunroof and tinted glass to keep car cool.

Keep Your Car in Shape: Maintaining your vehicle in top working condition saves you fuel and money, and reduces long-term maintenance costs while minimizing harmful emissions.