Masturbation

Warning: When attempting this position, make sure the car has not been driven recently and is completely cool.

Take an unrolled condom, slip the end inside the exhaust pipe and stretch the opening over the end of the pipe, or use a plastic bag secured around the opening with a rubber band. Squirt in some lube, insert your penis, and fuck your car.

Warning: When attempting this position, make sure the car engine is off and the parking brake is engaged.

Straddle the gearshift with one foot on the floor on either side of it. You may also be able to straddle it in a kneeling position, with one knee on each front seat. Raise yourself up and lower yourself down onto the gearshift until it penetrates you, or if you prefer, rub yourself back and forth against the knob and shaft to masturbate. Use your legs to raise yourself up and down or rock back and forth. Slip a condom over the gear knob for easy clean up.

Cut a hole through the upholstery of your backseat about the same size or little smaller in diameter than your cock (you won't want to do this if you have leather seats). Carve a hole into the foam deep enough to accommodate your erect penis. Lay across the backseat and hump the hole. Use a condom or insert a plastic bag into the hole to avoid creating a spunk-filled waste dump in the cushion. Conceal hole with a seat cover when not in use.

Mount a large dildo with a flanged base to the front bumper of your car using bungee cords or tie-down straps to secure it. Or use a dildo with a suction cup base and apply it directly to the bumper. Step up onto the bumper and plant your feet wide on either side of the dildo, leaning forward onto the hood for balance and support. Lower yourself onto the dong, insert it, and bounce up and down. When you're done, remember to remove the dildo from the bumper, unless you want to attract attention while driving.