There are several things that happen to your car’s structure and chemistry when you let it sit for too long. Such things include gaskets and seals becoming brittle, flat and brittle tires, drained battery, gummed up fuel, rust, and engine oil deteriorating.

There are a lot of other things that can happen, but these are the main ones to be concerned about. Let’s discuss each possible issue and how/why it happens to your car when you let it sit:

Gaskets and seals are an extremely important component to a car. Without them, there would be leaks all over the place and your car would cease to function because it would run out of fluid very quickly. If you use a rubber band frequently, their life-span is a lot longer because they’re being used for what they were made for. But if you let a rubber band just sit, it becomes brittle and will snap at any little pull. Gaskets and seals works the exact same way; when they aren’t used and exercised in a way they were meant to be used, they break down and don’t function the way they’re supposed to.

Tires on a car work similarly to gaskets and seals; if they’re not used, the rubber on them becomes ineffective. They get cracks and holes and will eventually get flat spots because air is escaping from the cracks. If you let a car sit on a flat spot on the tire, you’ll need to just throw out the tires entirely and get new ones; you cannot revive a tire with an old flat spot.

A drained battery will probably be your first issue you’ll have after letting a car sit. This is especially prevalent if you live in colder climates because batteries have a difficult time recovering from cold temperatures when they’re not used. There is also a phenomenon called “parasitic drain” which is a circumstance where the car’s computer and/or poorly grounded wires cause a slight and slow discharge over time.

Believe it or not, it is actually possible for your gasoline to go bad. If gas is not held in an air-tight container (which a car gas tank is not air tight), the oxygen reacts with the gas and destabilizes it and causes it to become a gel-like material. You may also notice a bad smell coming from your gas tank. If your gas becomes like this, it becomes unusable and you may not even be able to start your car.

Weirdly enough, rust actually forms a lot faster on cars when they aren’t used. Regularly driving your car actually prevents, or slows down, the formation of rust. This is because when cars are stationary, the oxygen and iron have a way better chance of reacting and creating rust as compared to high speed environments when the car is in motion.

The oil in your engine deteriorates a lot faster when it’s not being used. A lot of people assume that because they don’t use their car that often, especially if they have a classic car, that means they don’t need to change the oil as frequently as they would if they regularly drove their vehicle. It’s actually quite the opposite. Again, when this substance isn’t used the way it was intended to, it breaks down over time and loses it’s lubrication and cooling properties, thus giving less lube to your engine when you start your car.