We don't expect you to buy and drive a solar powered
car like this one from Swatch anytime soon but here are some Gas Mileage
Tips that can help you safe money and stress on the environment.

Solar Powered Car
These tips are thanks to fueleconomy.gov and
here
on their website you can find even more.
Drive Sensibly
Aggressive driving (speeding, rapid acceleration and braking) wastes gas.
It can lower your gas mileage by 33 percent at highway speeds and by 5
percent around town. Sensible driving is also safer for you and others, so
you may save more than gas money.
Keep Your Engine Properly Tuned
Fixing a car that is noticeably out of tune or has failed an emissions
test can improve its gas mileage by an average of 4 percent, though
results vary based on the kind of repair and how well it is done.
Fixing a serious maintenance problem, such as a faulty oxygen sensor, can
improve your mileage by as much as 40 percent.
Commuting
If you can stagger your work hours to avoid peak rush hours, you'll spend
less time sitting in traffic and consume less fuel.
If you own more than one vehicle, drive the one that gets the best gas
mileage whenever possible.
Consider telecommuting (working from home) if your employer permits it.
If possible, take advantage of carpools and ride-share programs. You can
cut your weekly fuel costs in half and save wear on your car if you take
turns driving with other commuters. Many urban areas allow vehicles with
multiple passengers to use special High Occupancy Vehicle (HOV) lanes.
Here is another resource for Tips for Saving Fuel from Cars.com