Almost everyone with a collector car puts it away for the winter. For some, putting a car away for the winter is as simple as driving into the garage and closing the door. For others, there is an elaborate winter storage ritual. I recommend that each car be maintained with plan for scheduled preventive maintenance plan, which should at the very least follow the manufacturer's recommended maintenance outlined in the vehicle's owner's manual.

Ideally, your car should be kept indoors or at least under a carport roof on a concrete floor. This minimizes the vehicle's exposure to moisture, contaminants, and vermin.

The following procedure is for winter storage (4-6 months) where the car is put away in the fall for use again in the spring.

Procedure Notes
Change the oil and filter

I recommend the use of heavy duty engine oils (HDEO) in vehicles, especially those without catalytic converters. Older passenger vehicles commonly used a 30-weight engine oil (SAE 30, 10W-30) and generally a modern 10W-30, 5W-30, or 0W-30 HDEO may safely be used. The additives in modern HDEOs are designed to resist sludge and corrosion and are much better than the early detergent motor oils.

  • For cars that are normally NOT driven on short trips (i.e., the engine oil does NOT reach operating temperature), it is sufficient to change the oil on the maintenance schedule.  Engine oil generally takes a lot longer to get hot compared to coolant and the temperature depends on RPM, load, and viscosity.
  • For those vehicle regularly driven mainly on short trips, it is best to change the engine oil and filter in the fall.
  • Corvair Oil Recommendations (Bottom Line Recommendation #22): "If you are not going to use the car for 2 months or more, change the oil first. Change it, run the engine a minute to circulate the oil, and turn it off. Engines stored with used oil will suffer from corrosion of the bearings from the reduced anti-corrosion additives and small contaminants trapped in the bearings. The new oil will clean and protect until you are ready to use the car."
Fill the fuel tank with fresh, ethanol-free gasoline.

Fill the tank to reduce the air volume in the tank above the gasoline, which reduces the likelihood of any moisture in the fuel from condensing as ambient temperatures drop. Although the ethanol in modern (E10 - 10% ethanol) gasolines will absorb condensed moisture in the tank (like gas line antifreeze), its hydrophilic nature means that it draws moisture out of the air, thereby making the situation worse. Often ethanol-free gasoline is a premium grade but is not necessarily so.

Add a fuel stabilizer (like STA-BIL) to slow down the rate at which gasoline becomes stale. The Gold Eagle literature for standard red STA-BIL states that it is safe for ethanol fuels (up to 85% - E85) and will keep fuel fresh for up to 12 months. Gold Eagle (and other fuel stabilizer manufacturers) has other fuel stabilizer products including a marine version for additional corrosion protection.

Fuel becomes stale for 2 reasons:

  • The lighter components evaporate, thereby leaving behind the heavy components.
  • The fuel oxidizes from exposure to air, thereby forming gums and varnishes.

Stale gas can plug up carburetors and can be difficult to ignite in the engine. It is better to dump stale gas (as hazardous waste) and use fresh than to try to burn it as fuel.

Verify coolant strength & life

If you've been following a scheduled maintenance program for your car, there is no need to replace your coolant for the winter. Regular green ethylene glycol antifreeze has a lifespan of 2-3 years, regardless of mileage. Modern universal (safe for all colours) antifreeze is now typically long-life with a 5-year lifespan. Plan to do a flush & fill at a time in the year that is most convenient for you and stick with it.

Ethylene Glycol does not wear out but it is the corrosion inhibitors that become depleted. A flush & fill removes any sediment in addition to allowing you to use fresh coolant. For vehicles that have had a poor maintenance history, it would be good to do a chemical flush using a citric acid or oxalic acid cleaner such as Gunk C2124). Pure citric acid is readily available local DIY wine shops and oxalic acid is more commonly known as wood bleach. Make sure the flush water runs clear (from the block drains and the rad) as there could be a lot of precipitate resulting from the chemical flush.

If there are no cooling system leaks, the strength you started off with should remain constant over the life of the coolant. It does not hurt to check its strength with a hygrometer, especially if you've had to top off the rad. As long as the strength is strong enough to have a significantly lower freezing point than your lowest expected winter temperature, you should be fine.

Inflate the tires to proper pressure.

If your tires have a slow leak, it is possible for the tire to become flat in storage. Repair any leaks and inflate the tires to the recommended pressure. Do not exceed the tire manufacturer's maximum recommended pressure moulded into the tire's sidewall.

Clean and wax the car.

While it's nice to have a clean and freshly waxed car for storage, it is more important that the underside of the vehicle is cleaned to reduce the possibility that that dirty areas will rust from constant contact with moisture. Give the underside of your vehicle a thorough rinse to remove any accumulated moisture-retaining dirt.

It is also important to clean the inside of your vehicle to ensure that interior debris won't decay or otherwise deteriorate. This will keep your car smelling fresh and the carpets clean.

Place a plastic sheet of vapor barrier under the car.

The common internet wisdom is that there must be a vapor barrier (plastic sheet) between the concrete floor and the vehicle. This is to prevent moisture from collecting underneath when the concrete sweats. The sweating would occur when the cold floor is exposed to warmer and more humid air so that the moisture would condense onto the cold floor. A concrete floor with plastic sheet on top would instead have the humidity condensing on the plastic sheet so not much would be gained by this.

I'm not sure how a vapor barrier on top of a concrete floor would work since concrete is not really that permeable and would therefore not transfer very much moisture from below very well. The US EPA does have recommendations for controlling moisture from concrete floors but their recommendation is to have a capillary break underneath the slab. To control moisture over soil, the EPA recommends a plastic sheet extended to each wall, secured with furring, and sealed with caulk. See Capillary Breaks.

A concrete floor would drier than a gravel or dirt floor and is preferable for vehicle storage. Regardless of what floor is below the vehicle, it would be better for the floor to well ventilated so that any moisture would be vented away. Just make sure that the ventilation system is screened to prevent vermin access.

Open a window slightly if stored indoors.

This allows any moisture within the interior to escape to reduce the likelihood of having a musty odor in the spring. Keep the opening small enough to prevent small animals from entering.

Use a battery maintainer.

It is not necessary to remove the battery for warm storage indoors. A battery maintainer/tender or trickle charger will keep the battery fully charged to maximize its life. For older cars without continuous parasitic loads (electric clock, onboard computers, etc), a battery maintainer isn't necessary if the car will be stored for less than a month.  For newer cars, it's probably safer to use a trickle charger if they're not expected to be driven for 2 weeks or more.

Keep the wiper blades off the windshield.

Place a piece of plastic wrap on the windshield under the wiper blades. You could also remove the wiper blades or possibly park them in an up position to prevent the rubber from sticking to the glass.. Removing the wiper blades runs the risk of scratching the glass if the windshield wipers are inadvertently turned on.

Plug rodent access holes

Put a rag in places like the tailpipe and the air cleaner's air inlet.

Coat the cylinders with oil.

Remove the spark plugs and spray a small amount of oil into the cylinders to prevent corrosion, then reinstall the plugs. For storage over the winter, it is probably not necessary to put oil inside the combustion chambers but it can't hurt. Too much oil can potentially affect the catalytic converter or cause the engine to be hydrolocked.

Before replacing the spark plugs, it would be useful to slowly turn the engine over (by hand if possible) to distribute the oil over the cylinder walls. Using the starter motor could cause the oil to spray out of the spark plug holes, leaving an oily mess on the fenders.

The alternative to putting oil in the spark plug holes is to use a fogging spray. Follow the directions on the can.

Place the car on on axle stands to avoid flat spots in the tires.

Extended storage with the tire remaining in one spot will cause the tire to develop a flat spot. Depending the tire's construction, driving the car in the spring will remove any flat spots that might have developed. Putting the car up on blocks will eliminate the possibility of developing flat spot. It will also ensure that the tire does not become damaged from being flat if a slow leak develops over the winter.

Release the parking brake.

This minimizes the possibility of the brake shoes sticking to the drum. In a manual transmission car, use wheel chocks if necessary to keep the car from rolling away.

Place a note to yourself on the dashboard.

If there any things that need doing to bring your car out of storage in the spring, leave a note for yourself to ensure that these things are not forgotten. This would for things like removing the battery maintainer, removing rags, and removing the wiper blade plastic wrap.

Lock the doors.

If there is any possibility that someone could access your vehicle while it's in storage, lock the doors to reduce this temptation.

Use a car cover only for outdoor storage.

There is no need for a car cover in a secure indoor location unless the location is very dusty. Installing and later removing it has the small possibility of damaging the paint or other exterior parts of the car.

Drain the windshield washer fluid tank

Windshield washer fluid typically contains methanol (aka, methyl hydrate, methyl alcohol). Over time and especially in summer heat, the alcohol could evaporate, leaving behind a fluid with an insufficient freeze point.

If your car is not driving in winter conditions, you should be using a summer windshield washer fluid with a lower concentration of alcohol and more detergents than winter windshield washer fluid. Dump the old drained fluid into your daily driver and put fresh summer fluid in your classic in the spring.

Rustproof your car

There are many types of rustproofing chemicals available for vehicles. While the heavier stuff (like Dominion Sure Seal Anti-Corrosion Material, PN ASS512A) that is suited for your winter car will work fine on your summer car, you can use a lighter rustproofing (like Krown PN T40) that undercoats your car with a oily coating instead.

There will often be some drippage from the undercoating. You can either rustproof your car during the summer or park it on old carpet or cardboard to keep the floor clean underneath.