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10. Use the landscape to your advantage.
If the road goes up and down, don't try to maintain a constant speed. Let your car accelerate down the hill, so its inertia will help it climb up the next hill, and let the speed decrease slightly while you are going up. Of course you have to coordinate this with the traffic flow.

11. If you have several cars, use the one with the best gas mileage for daily commuting.
That car is usually easier to park, too.

12. Plan your route to avoid traffic jams.
Because you can't avoid excessive idling, braking and acceleration while in a traffic, traffic is usually responsible for a big chunk of your gas consumed. You might avoid jams sometimes however, if you learn traffic patterns in your area and use them to your advantage.