A Note on the Calculations: 

Your mileage will vary.  Governments and automakers estimate fuel mileage savings by percentage -- do x and you'll get five percent better fuel

mileage.  I wanted to know what they meant in real dollars, so I used the average mileage Americans actually got from their cars in 2007 (22.4 mpg, according to the Bureau of Transportation Statistics) and boosted it by the percentage each tip should gain.  I've assumed you spend 55 percent of the time driving in the city and 45 percent driving on the highway.  I borrowed those assumptions from the formula EPA uses to calculate the mileage of new cars.

Using the average price of a gallon of gas as of June 12  ($4.05, according to AAA) and assuming you drive 15,000 miles a year (according to EPA estimates), I calculated what each tip would save in a year.  The numbers aren't a perfect prediction -- I have no idea what you drive, or what's in your trunk -- but they do provide an interesting perspective.  Here are ten easy ways to put the math to the test and put some more cash in your wallet.

1.    Get that "Check Engine" Light Checked Out:

引擎灯一定不可亮

Possible Savings: Off the charts

A faulty oxygen sensor -- a fairly common cause of those unexplained "check engine" lights -- can actually cost you up to 40 percent of your engine's performance.  If the light's on, make the appointment now.  It could pay for itself very quickly.

2.    Check Your Tire Pressure:

车胎压力必须保持均衡

Possible Savings 133.9 gallons/year ($542/yr)一年可节省大约542元

According to some government estimates, the average driver could boost their fuel efficiency by 25 percent just by keeping their tires inflated.  That's often a free, or cheap, repair.  On my way to work, I pass two gas stations with air compressors I can use for free, and three -- apparently owned by cheapskates -- that take quarters. 

3. Change Your Air Filter:

按时置换空气过滤器

Possible Savings 60.9 gallons/yr ($247/yr)一年可节省大约247元

Gas is half of the combustion equation.  Air is the other half.  A clogged air filter can rob 10 percent of your engine's efficiency.  A new air filter can get that 10 percent back -- usually for under $15。

4．Drive 60 on the Highway, Not 75:

高速公路上的速度60为最佳速度

Possible Savings: 57.8 gallons/year ($234/yr)一年可节省234元

On the highway, stay close to the speed limit, and keep your speed as constant as traffic allows.  Most cars reach optimal gas mileage at about 60 miles per hour.  Speeding up increases wind resistance against the car, making the engine work harder and burn more gas.  According to the EPA, each 5 mph over 60 that you drive decreases fuel efficiency by up to seven percent.

4． Turn Off the A/C:

尽量不开空调

Possible Savings 31.9 gallons/yr ($129/yr)一年可节省129元

Some air conditioners rob an engine up to five percent of its fuel economy.  There is some controversy about this one -- many newer cars are able to compensate for the energy used by an air conditioner and don't suffer the same penalty for keeping cool.

5。Get Your Engine Tuned:

定期维修引擎

Possible Savings 25.8 gallons/year ($104/yr)一年可节省104元