Don’t speed up just to slow down. If you lean on the accelerator when the light turns green, then again on the brake one street down, you’re hurting both your car and your gas mileage. Instead, go lightly on the accelerator and coast where possible. If you’re bumper-to-bumper, improve your fuel economy by slipping the car into neutral instead of constantly riding the brake. (This doesn’t apply to hybrids which typically shut off the gas engine when stopped in traffic.) And don’t try to get around the city on less than a quarter tank. Not only are city gas stations expensive, they’re hard to find.