Leaving a car for a month or more: preparation and checks on return

A car that stands wears differently from one that is driven — but it does wear. A month of unprepared storage costs more than a month of ordinary use.

What deteriorates while standing

The battery. Quiescent current discharges it within weeks; a deep discharge shortens its life irreversibly; covered in the parasitic drain article.

Brake discs rust — a film within a month, and pitting within six.

Tyres develop flat spots from standing in one position.

Fluids age by the calendar: oil, brake fluid, coolant.

Rubber — seals, boots, and hoses dry out.

Fuel ages and produces condensate in the tank.

Rodents — they chew wiring, and that is a genuine cause of expensive repairs on stored cars.

Preparing for storage

Wash and dry it — salt, droppings, and sap will attack the lacquer within a month.

Fill the tank to around three quarters — less empty space means less condensate.

Change the oil if it is nearly due: used oil with combustion products is more aggressive.

Inflate the tyres slightly above normal — that reduces deformation.

Do not use the handbrake — the shoes bond to the discs; leave it in gear or in P with a chock; covered in the handbrake article.

The battery: disconnect a terminal or connect a maintenance charger. Disconnecting resets adaptations and settings; covered in the battery replacement article.

Screen the intake and exhaust against rodents if storage is rural.

Do not cover a dirty car; covered in the car cover article.

What to do on return

1. Inspect under the bonnet — rodent traces, nests, chewed insulation.
2. Check every fluid level.
3. Tyre pressures — set them to specification.
4. Do not start immediately with a disconnected terminal — reconnect and let the modules initialise.
5. Read the codes — after storage they often appear on their own.
6. The first few metres carefully: the brakes are rusty and the first applications may be weak.
7. Dry the brakes with a few applications.
8. Check quiescent current a few days later.

About adaptations

After a terminal disconnect the car drives differently for a while: the module relearns idle and the gearbox relearns shift points.

That is normal and settles within a few dozen miles. There is no need to panic and visit a workshop on day two.

What is worth doing: read the codes and let the readiness monitors run back, especially with an annual test coming; covered in the readiness monitors article.

In short

• Standing harms a car differently from driving, but it does harm it.
• Do not leave it on the handbrake — the shoes bond to the discs.
• A three-quarter tank reduces condensate.
• A maintenance charger beats a disconnected terminal: settings survive.
• After storage the first brake applications are weak — dry them.

Download the app — voltage, codes, and monitors after storage are read with an ELM327 adapter over Bluetooth SPP on Android.