Leaving a car unused

What you need to do if you're not going to be using your car for a few weeks or months

Don't remove a battery lead unless you know the radio code

Don't remove a battery lead unless you know the radio code

If you are going to leave your car unused for a while there are a few simple things you can do to make sure that it will be in good condition and ready to use when you get back. What you will need to do depends on how long the vehicle will be left.

We've broken it down to 'up to a month', 'one to three months', and 'more than three months'.

Remember that, since the introduction of Continuous Insurance Enforcement (CIE) in 2011, your car must remain insured while not being used unless you make a Statutory Off Road Notification (SORN).


Read this first

  • Don't remove a battery lead unless you know the radio code.
  • On-board computers can be affected by long term disconnection of the battery – check the handbook or contact the manufacturer.
  • Don't let plastic covers rest on the paintwork. Flapping covers can damage paintwork.
  • Make a note of what you've done to the vehicle and put it in the car as a reminder when you need to use the car again.
  • For long periods or high value cars think about using a commercial storage company.
  • You could simply arrange for someone to use the vehicle once or twice a month in dry weather – providing insurance, tax and MOT, etc. are in order.

One month

If you're not sure if the battery will stay charged,  a 'smart charger' is a great investment. These only charge the battery when it needs it and can be left connected without risk of overcharging.

  • Get the anti-freeze concentration checked – particularly in Winter
  • Leave the handbrake off if parked off road – chock the wheels securely first
  • Leave windows partially open for ventilation – but only if the car's is in a secure garage
  • Unpainted metal parts can be sprayed with WD40 to reduce corrosion – don't spray rubber or trim

Up to three months

In addition to the 'one month' points:

  • Clean, and polish the car – hose under wheel arches to remove mud but make sure it's dry before putting it away
  • Invest in a 'smart charger' that can be left connected to the battery without risk of overcharging
  • If you suspect dampness, raise or remove carpets and dry thoroughly
  • Check that drain holes in doors, sills and bulkhead/heater are not blocked
  • Lift wiper arms so that the blades are clear of the glass
  • Consider a refund on your road tax by declaring Statutory Off Road Notification (SORN). More details on the DVLA website
  • You may also be able to reduce your insurance cover to fire and theft only
  • If the car's in a garage, make sure there's plenty of ventilation

As an alternative to ventilation you could seal the garage and use a dehumidifier – cheaper and probably better than heating. (A dehumidifier will need a low-temperature shut-off though as it can't work below about 4C.  Corrosion is not a problem in very cold weather, provided the car is dry and free from road salt.

More than three months

In addition to the one month and three month points:

  • Carry out an 'oil and filter' service
  • Slacken auxiliary drive belts – alternator, power steering, air conditioning, etc. Don't slacken the camshaft drive belt
  • Lubricate locks with a suitable lock oil
  • Spray under the bonnet, around the battery box, under the wings and the metal in the boot area with WD40 or similar
  • Lift the vehicle onto blocks or stands to raise the wheels clear of the ground and unstress the tyres
  • If you can, remove the wheels and store them flat in a cool dark place

Fuel matters

Petrol will stay fresh in a sealed container for about a year but starts to degrade in as little as a month when exposed to the atmosphere – the lighter more volatile fractions evaporate, lowering the fuel’s octane and making starting harder.

Petrol exposed to the atmosphere will start to oxidise over long periods too, producing gum and varnish deposits on fuel system components.  This is more likely to be a problem with older carburettor fuel systems than with sealed fuel injection systems.

Stored diesel should be OK for up to a year, depending on temperature but will start to oxidise over longer periods, producing gum and other sediments that can quickly block filters when the engine is run again.

Bear in mind that diesel fuel specifications change through the year - fuel bought in summer will be much more susceptible to waxing in cold weather than winter diesel formulated to give protection down to at least -15C.

Fuel tank

Unless you are able to ensure a dry stable environment, for periods over a month or so it is best to store a vehicle with a full tank of fuel to reduce the space for water to condense.

Condensation in the fuel tank can be a serious issue:

  • Corrosion can seriously damage the tank, though most modern tanks are plastic, and fuel lines.
  • Current petrol contains up to 5% Ethanol which has an affinity for water. In extreme cases phase separation can occur where the Ethanol and water separate and drop to the bottom of the tank
  • Water allows bacteria and fungal growth in diesel which can require fuel tank removal and cleaning to eradicate.

For long term storage, particularly of older (pre-injection) vehicles, consider using a fuel stabiliser additive. Stabilisers are widely used for garden machinery, and other petrol-powered equipment left unused for a couple of seasons as well as motorbikes taken off the road over winter.  Follow the instructions carefully.

Starting a car left unused for a long time

The work required to start a car that's not been used for a long time will depend to some extent on how well the car was prepared before being put into 'storage'.

  • Check tyre pressures
  • Check that nothing's nesting under the bonnet or has chewed through the pipes/hoses
  • Re-tighten any drive belts loosened when the car was put away
  • Check all fluid levels before starting – change the oil once the car's running
  • Stale fuel could be a problem – hopefully there's not too much in the tank so that fresh fuel can be added and can get through to the engine
  • Taking the plugs out first and turning the engine over is a good idea as this will reduce the load on the engine whilst the oil is redistributed
  • Check brake operation including the handbrake – the brakes will probably be seized on if the car's been left with the handbrake applied. Try engaging a gear and driving gently, otherwise dismantling may be necessary

Arrange a full service once the car is running again.

MOT

You can only drive a car without an MOT on the highway if it is being driven by prior arrangement to a garage for an MOT.

If garage work is required before the MOT then the car should be moved only by truck or trailer.

(24 December 2013)