What happens if a car is left unused for months?

Several things degrade at once, and most of them are avoidable with a little preparation.

The battery is the usual first casualty. Modern cars draw a small current continuously for alarms, keyless entry and electronic modules, and a battery left to discharge slowly can be flat within weeks and permanently damaged after a few months. A battery maintainer, or disconnecting the negative terminal, prevents it.

Tyres develop flat spots where the weight of the car rests, particularly in cold weather. Short-term flat spots usually work out after driving; long-term ones may not. Inflating slightly above normal pressure before storage reduces the risk.

Brakes seize. Discs corrode and pads can bond to them, and a handbrake left engaged for months is a common cause of a car that will not move. Chock the wheels and leave the handbrake off.

Fuel degrades. Petrol begins to oxidise and can leave gum deposits after several months; a fuel stabiliser and a full tank — which reduces the air space where condensation forms — both help.

Fluids and seals. Oil drains away from surfaces, and rubber seals dry out. Occasional running is often suggested, but a brief idle is worse than nothing: it does not reach operating temperature, so it generates condensation in the exhaust and oil without burning it off. If you run it, drive it properly for twenty minutes.

Rodents are a real and frequently overlooked problem, chewing wiring and nesting in air intakes.

Also check what insurance and road tax require for a vehicle kept off the road, which differs by country.