It's full of practical advice without using a lot of mechanical jargon. I added thoughts in italics.
Follow the Recommended Maintenance
A vehicle that is well maintained means it will operate with greater efficiency. Fouled spark plugs, a dirty air filter or clogged fuel filter will all affect your fuel economy. According to the U.S. Department of Energy (DOE), replacing a clogged air filter can increase your mileage by 10 percent, while replacing an oxygen sensor could result in an improvement as high as 40 percent.
Keep Your Tires Properly Inflated
Underinflated tires require more energy to roll, which translates into more frequent fill-ups. You can improve your fuel economy by about 3.3 percent if you keep your tires inflated properly, according to the DOE. The psi number noted on the sidewall of your tires is the maximum pressure of the tire and is not the proper inflation level for your car. Your vehicle manufacturer will list the recommended tire pressure in your owner's manual or a sticker on the doorjamb of the driver-side door. Buy a tire-pressure gauge and check your tires monthly, adding air as necessary. (I never realized the #s were different!!)
Take a Load Off
Heavier vehicles require more energy to move, so carrying around excess weight will also affect your mileage. Empty out your trunk (or even your backseat) of unnecessary items. An extra 100 pounds in the trunk will reduce your fuel economy by 1 to 2 percent in the typical vehicle. (So minivan moms, that probably means we should take out the extra seats we rarely use!)
Don't Drive Aggressively
We're not talking road rage here, but the type of driving many people do when they are in a rush. Mashing the accelerator pedal from a stoplight, braking hard and speeding all contribute to a decrease in fuel economy. Give yourself extra time to get to your destination and think "steady and smooth" as you drive. On surface streets, driving at the speed limit will give you mostly green lights, which improves your gas mileage as well as reduces the wear on your brakes. On the highway, the DOE says that every 5 mph you drive over 65 mph represents a 7-percent decrease in fuel economy.
Use Cruise Control — Selectively
Using cruise control can improve your gas mileage by helping you maintain a steady speed, but only if you are driving on mostly flat roads. If you are driving in hilly terrain, using cruise control typically causes your vehicle to speed up faster (to maintain the preset speed) than it would if you were operating the accelerator yourself. Before you push that cruise control button, think about the terrain ahead.
Keeping your car washed and waxed improves aerodynamics and therefore affects fuel economy. Engineer Tom Wagner, Jr. reported to Stretcher.com (as in stretching your dollars) a 7-percent improvement in fuel economy, from 15 to 16 mpg, during a 1,600-mile road trip. (Oops - I'm in trouble here! I usually let mother nature 'wash' my car!)
Avoid Excessive Idling
When a car is idling, it is using fuel, yet not going anywhere. This translates to 0 mpg. When you leave your car running while you are waiting in line at the drive-thru, or as you wait outside your kids' school, you are wasting fuel. It is more efficient to turn the engine off while you wait and then restart the car. If that's not practical (like in the line at McDonald's), then park the car and go inside instead.
Think Before You Vent(ilate)
Running your air conditioner does cause your vehicle to consume more fuel, but driving with your windows rolled down can be even worse due to the increase of drag on the vehicle. If you are driving slowly, such as around town or in city traffic, then you are better off leaving your windows open, if at all possible. For highway driving, roll up the windows and turn the air conditioning on.
Combine Your Errands
A little planning can make a big difference in fuel economy. When your engine is cold, it uses more fuel than when it is warm. Combining errands can improve your gas mileage because your engine will be warm for more of the trip. It might also mean you travel less total miles. According to the DOE, several short trips all begun with a cold start can use twice as much fuel as a single, longer trip that covers the same distance. (That's a whole new reason to ask your neighbor if he needs anything from the grocery store when you're already going!)
Thanks for the tips Tara!