We've heard many people say they let their cars sit for months in a garage with no problems, but you're better off driving it a couple of times each month and for at least 10 miles, with some speeds over 50 mph if possible. You not only want your engine to get fully warmed up but for the entire car to get some exercise as well.
Letting a car idle for 10 minutes will get the engine up to normal operating temperature but accomplish little else. Driving the car for several miles wakes up the transmission, brakes, suspension, power steering, climate system (including the air conditioner) and all the fluids, seals and gaskets for those components that have been on a long snooze.
Batteries slowly lose their charge when they sit idle, and starting the car will drain it even more. That is one reason you want to drive several miles afterward, so the battery has a chance to recharge. If a car sits parked for a month or more, the battery may lose so much power that it will need a jump-start — or a charge before the engine will start. To be sure your car will always start, consider a battery tender as described in our guide, "How to Store Your Car for Winter." Unlike the rechargeable batteries in electronics, conventional car starter batteries don't like to cycle deeply, so keeping them topped off could improve their longevity.
Here are more reasons not to let your car sit for several weeks or longer:
Tires slowly lose air under all conditions but especially during cold weather. As they do, the weight of the car keeps pressing down on the tires, which causes flat spots to develop on the segments sitting on the ground. Driving the car and adding air if necessary will usually make the tires round again, but letting the vehicle sit for extended periods on underinflated tires can cause permanent flat spots that you will be able to feel and hear when you drive.
Rodents might take up residence under the hood or even in exhaust outlets. If they get hungry, some may munch on the wiring harnesses and other parts made of soy and other organic materials that are used on modern vehicles.
Moisture can collect in the gas tank (especially if it isn't full) and in the oil over time, and that can lead to corrosion.
