Storing a classic car for a year or more

Over a winter, most things that go wrong with a stored car are slow enough for a spring check to catch them. Over a year or more, several pass that point. Petrol is well past its useful life, glycol brake fluid has taken up more water, tyres have aged further, seals no longer wetted by fuel have dried, and a neglected battery may be beyond recovery. The British Tyre Manufacturers' Association (BTMA) explains that flexing in normal use helps protective additives reach the surface of a tyre, and that this process is greatly reduced on vehicles used infrequently. Long-term preparation slows all of this and makes the car's return predictable; it cannot stop it. Expect more work when the car comes out: see recommissioning a long-stored car.

A long stay magnifies whatever is wrong with the garage. Measure the humidity for a few weeks and deal with damp and rodents before the car goes in: see damp and condensation and mice and rats. If your garage cannot be made dry, a commercial storage firm may suit a long stay better; the questions to ask are on our storage hub. Tell your insurer where the car will be kept.

What the FBHVC advises

The Federation of British Historic Vehicle Clubs (FBHVC) warns that storing petrol containing ethanol, even over a winter, can lead to corrosion in fuel systems. For an extended lay-up it recommends replacing E10 with ethanol-free petrol, which some suppliers sell, and, where that is not available, draining the carburettor float bowls, because petrol left in them evaporates and can leave a corrosive residue of water and ethanol. It also warns against leaving fuel systems dry, because seals and gaskets can shrink and crack, and recommends a corrosion inhibitor additive in E5 and E10 petrol.

Full, empty or drained?

For a winter, sources disagree about tank level; our winter lay-up page sets out both views. For a year or more, what matters more is which fuel is in the system:

• Ethanol-free petrol, tank filled. This follows the FBHVC's preference and, in a steel tank, leaves little air space for moisture. Run the engine on it before storage so the pump, lines and float bowls hold it too.
• E5 or E10, float bowls drained. If you cannot get ethanol-free petrol, drain the float bowls as the FBHVC advises, using the drain plug or by removing the bowl as the workshop manual describes.
• Tank drained. Some owners empty the tank completely for very long storage. That removes stale fuel, but the FBHVC warns against leaving fuel systems dry, because a dry system can corrode and its seals and gaskets can shrink and crack. If you drain the tank, ask your marque club or a specialist how to protect it.

Whichever you choose, plan to replace the fuel when the car comes out. The FBHVC notes that ethanol is a good solvent that can loosen old deposits in tanks and lines, so check fuel filters after fresh fuel goes in.

Stabilisers. These additives are sold to slow the ageing of petrol, but the evidence is thin: the RAC does not normally recommend them, and a restoration specialist quoted by Hagerty UK had yet to find one that works. If you use one, it is no substitute for fresh fuel later.

Safety. Drain fuel outdoors or with the doors fully open, away from any source of sparks or flame, into suitable containers (the HSE limits are on our fire safety page). A garage can drain the tank for you, as the RAC suggests. Never pour old petrol down a drain: councils take it at household waste recycling centres, but check with your local site first.

Change the oil and filter before storage and run the engine until fully warm so clean oil coats the internals. Hagerty UK also advises changing the oil and filter before starting any car stored for more than a year, because acids and moisture build up in storage. Budget for both.

Some owners put a small amount of oil into each cylinder through the spark plug holes before long storage, as engine oil or a sprayed "fogging" oil, to leave a film that resists rust on the bores and rings, particularly in cylinders where the valves stand open.

• For. Recommissioning guides commonly advise oiling the bores before a long-stored engine is first turned, and a rusted bore or stuck ring is an expensive repair.
• Against. Oil does not compress, so too much in a cylinder can stop the engine turning, and forcing it risks damage. The film may drain away over months, and we found no reliable figure for how long it lasts. Excess oil fouls plugs and must be cleared before the first start, usually by spinning the engine on the starter with the plugs out and the ignition disabled.

Our view. It is not needed for a winter in a dry garage. For several years, or a garage that is not reliably dry, a small amount of engine oil in each cylinder, with the engine then turned slowly by hand to spread it, is a reasonable precaution. Note it on the reminder you leave on the steering wheel, and ask the marque club first if you are unsure.

• Tyre cradles or cushions spread the load without lifting the car. Footman James suggests them for long-term storage.
• Axle stands take the weight off the tyres altogether. Place them on firm, level ground at the support points in the workshop manual, under the axles or suspension so it is not left hanging. Never rely on a jack, and never work under a car that is not properly supported.
• If the car stays on its wheels, raise pressures towards the sidewall maximum, never above it.

Note the tyres' date codes now (see recommissioning for how to read them). Plan to replace tyres that will be ten years old or more by the time the car comes out: the BTMA says some tyre makers recommend withdrawing car tyres over ten years old, and a classic tyre specialist quoted by Classics World says tyres over ten years old should not be on a car.

Leave the handbrake off and chock the wheels, as for a winter. Glycol brake fluids (DOT 3, DOT 4 and DOT 5.1) absorb water over time, which lowers their boiling point. Professional Motor Mechanic advises changing DOT 4 and DOT 5.1 at least every two years and DOT 3 every year. If the fluid will fall due during storage, change it when the car comes out rather than before. Silicone DOT 5 fluid behaves differently and must not be mixed with glycol fluids, and a few cars use mineral hydraulic fluid, which must not be mixed with either. Check the handbook or the reservoir cap for the type your car uses. Seals in calipers and cylinders can stick after long standing, so plan for a full brake check on recommissioning.

A specialist quoted by Hagerty UK recommends wiping silicone grease over every rubber seal once the car is washed and dried. Some owners slacken an adjustable fan belt so it does not take a set, with a tag to remind them to retension it; we found no authoritative guidance either way, so follow the workshop manual. Footman James suggests checking belts and hoses for wear or stiffness every month or two in storage. Keep the car away from electric motors such as freezers and compressors: Pirelli warns that electric motors generate ozone, which speeds up the ageing of rubber.

For a year or more, a conditioner designed to be left connected indefinitely is the simplest choice where the garage has a safe power supply; a Hagerty UK specialist notes that a disconnected battery will run down regardless. If you remove it instead, keep it cool, dry and frost-free. VARTA advises charging it to around 12.7 to 12.8 volts first, checking every two months and recharging at 12.5 volts or less.

Unless the workshop manual says otherwise, leave the system full of coolant of the correct type and strength, so the antifreeze protects it against frost and its corrosion inhibitors keep working. The FBHVC advises traditional inorganic additive (IAT) antifreeze for historic vehicles unless the car used another type when new, and replacing coolant within the antifreeze maker's interval. If it will fall due during storage, change it before the car goes in.

Prepare the interior as for a winter: clean, no food, moisture absorbers in the cabin and boot, windows closed if there is any chance of mice, and a convertible's hood up. Use a breathable indoor cover over a clean, dry car, never plastic sheeting. An airflow enclosure suits a long stay in a dry garage, but needs power all the time: if the fans stop for weeks, it becomes a plastic bag around the car. See damp and condensation.

Check it regularly

Carry on with the monthly check on our winter lay-up page for the whole period. Over a long stay, also check the battery voltage or conditioner every two months, look at belts, hoses and seals every few months, and keep a note of when fuel, oil, coolant and brake fluid will fall due.

Start it, turn it, or leave it alone?

Short idling does not warm the engine through, so water from combustion condenses in the engine and exhaust. Footman James advises against starting a stored car just to idle it, warning that a few minutes' idling can cause condensation in the exhaust; a lubricants specialist quoted by Hagerty UK supports starting from time to time only if the engine, and ideally the whole car, is thoroughly warmed through. For how to start it safely, see starting a car after storage. If the car is taxed, insured and roadworthy, a proper drive every month or two is the best exercise it can have. On a SORN and on stands, leave the engine alone. Never run an engine in a closed garage: the NHS lists this as a cause of carbon monoxide poisoning.

Some owners turn the engine slowly by hand every month or two instead, with the ignition off, believing it stops rings and valves sticking. It does not circulate oil under pressure, and we found no authoritative evidence for or against it. If you do it, turn the engine only in its normal direction and never force it.

• SORN. A car that is not taxed and insured must have a SORN. GOV.UK says a SORN does not need renewing and ends when you tax the vehicle again; the car must not be kept or used on a public road except to drive to or from a pre-booked MOT or other test. Our storage hub has the fines.
• Laid-up insurance. A SORN car need not be insured, but uninsured it has no cover against fire or theft. Hagerty UK describes laid-up cover as generally protecting against fire and theft but not road risks, third-party damage or breakdown. Check whether it covers rodent and accidental damage.
• V5C address. The keeper must keep the V5C address up to date, and GOV.UK says you can be fined up to £1,000 for not telling DVLA about a change of address. A house move during a long storage is when this is missed.
• MOT exemption. Storage does not affect whether a car qualifies. Under GOV.UK rules, a car built or first registered more than 40 years ago and not substantially changed does not need an annual MOT, though it must be kept roadworthy. The exemption is declared each time the car is taxed without a current MOT, so when you tax it again after a SORN you make the declaration then: online, by confirming the exemption when asked, or at a Post Office with form V112. A car that is not exempt will need a valid MOT before it can be taxed. Many owners of exempt cars choose a voluntary MOT after long storage.

General figures from our sources; your handbook and the product maker's advice come first.

After a year or more, treat the car's return as a recommissioning, not a spring start. Fuel, oil, brake fluid and probably tyres will need replacing, and the brakes need careful checking before the car moves under its own power. For a car that has only been laid up over one winter, our printable spring recommissioning checklist is enough.