Long Term Storage **NEW**

  • Battery - Disconnect the cable. Remove the battery if storage is not maintained above freezing. Use a battery maintainer, not a trickle charger. Best to store the battery outside the car. Don't close the door on the battery maintainer wiring. 
  • Fuel system - drain fuel if storing for more than 6 months. Not necessarily dry, but as low as possible. Use a fuel stabilizer, and run it in before draining the system. Drain it dry if going more than a year. 
  • Cooling System - change the coolant every two years. 
  • Engine Oil - Change every 3000 miles / every year. Changing just prior to storage rather than just after storage is best. 
  • Brakes - Flush the hydraulic system every two years. Leave the hand brake disengaged (off). 
  • Clutch Fluid - Flush the system every two years.
  • Lift Pistons (Doors, Luggage Compartment, Louvre - Leave everything open for longest life if the environment is safe (no critters or kids or dirty air). Removing the lift pistons is an option with the risk of causing other damage during the process.
  • Stainless - If using a car cover, remove and clean the car every 6 months. If you can't do this, leave the cover off (see discussion below).
  • Tires - Air to limit shown on tire label. If possible move the car a foot or two monthly while stored. 
  • Suspension - Don't do anything.
  • Interior - Treat the leather with a high quality leather preservative. Clean everything else. Don't leave anything on the seats.
  • Outdoors. Don't store a car outside. IF YOU MUST, don't store a car on damp dirt or grass. Ground should be paved and well-drained. Cover but keep it clean.
DETAILED VERSION for those who want to know why:
As with many collector-grade automobiles, DeLoreans are more often the owner's "third car", that is, a car for occasional pleasure driving use, car shows, etc. rather than being "daily driven". This means that, although the car isn't getting the wear and tear of a normal-use vehicle, the car is more likely to deteriorate from environmental issues than from "wearing out parts". In addition, the cars are more likely to be stored for long periods of inactivity, sometimes due to climate (parked for the winter), and sometimes due to lifestyle issues. In any case, it is important to store the vehicle properly to optimize its condition for continued use. The following suggestions apply to almost any car, with the possible exception of the fuel tank. 
What is long term storage? In short, anything more than a month. As the periods pass six months and a year, the preparation for the storage takes on more intensity. Once a car has been stored for more than two years, the owner is now dealing with "bringing a stored car back to life" which is the subject of a separate Knowledgebase article. 
This will break the car down into several systems. In general any part of the car containing fluids is the first part to need attention, but there are other items than can benefit from some foresight and preparation as you put the car away for a while. 
The DeLorean is notorious for having low parasitic electrical drains. Storage up to a month with the battery connected is about the limit of when it will start when you come back. It's best to disconnect the battery any time you don't know when you are driving it next.
For long term storage, we highly recommend removing the battery from the car. In the event of a malfunction of a charging device, or internal battery failure with a charger in place, the battery will boil over and acid will ruin large areas of carpeting. Always remove the battery if there is danger of freezing in the storage area. A charged battery will not freeze, but if the battery fails or discharges it will freeze and force out acid.
You may want to use a "battery maintainer" for long periods of storage. The battery will last longer. Do not use a cheap $10 "trickle charger" as they are notorious for overcharging and ruining batteries. A good maintainer is typically $50 and up.
Do not close the car door on the battery maintainer wiring. The bare stainless of the door is very conductive, and if the wiring gets abraded by the door it may short out the battery, causing the wiring to melt and ruin the carpet or even start a fire. Better to leave the door open or run the wire through and open window. Still best to remove the battery from the car.
Gasoline is the first fluid in the car to degrade with time. With the introduction of fuels laced with ethanol (grain alcohol) as early as 1980 in some locations, the shelf life of gasoline has shortened tremendously such that the effect of storing gasoline for as short as 6 months can be felt in how well the car runs. 
The DeLorean has a fully plastic gas tank, so corrosion of the tank is never an issue (unlike other older cars). The issue that we see is fuel degradation and contamination. The only way to prevent this is to remove as much fuel from the tank as possible when parking the car for extended periods of time, then adding fresh gas at the first start. There is no good way to run the fuel system completely dry, so before removing the fuel add the correct mix of a commercial fuel stabilizer such as Sea Foam or Sta-Bil brands, and run the engine long enough to circulate the mixture through the system (5-10 minutes is enough, but "fans on" is a good indicator). 
Even with this, a car stored for several years will likely have problems in the fuel injection system. The only way to avoid this completely is to NEVER store the car for over a year without cycling new fuel and stabilizer through the system. The real advantage to completely draining the system when parking the car for, say, 10 years, is that the restoration process will be a lot less work! The in-tank components will fare much better in a completely dry tank. 
The anti-corrosion agents in coolant break down over time. In general two years is a safe interval for cars that are operated periodically, an extra year or two is OK if the car is only run a few hundred miles a year. If you just ignore it, eventually the coolant will begin to cause corrosion in the engine and aluminum tubing of the cooling system due to electrolysis between the aluminum, iron, brass, and sometimes stainless parts of the system.
Contrary to what the advertising people would like you to believe, engine oil has a very long shelf life, typically up to 5 years in a sealed container. In a car, the conservative change interval is every 3000 miles or one year. Two years is probably acceptable if the mileage is very low, as long as there are not many instances of short-time running which can build up moisture in the oil that would boil out in longer run times. It is most important to changing the oil warm and at the end of a driving season. If dirty oil sits undisturbed for extended periods of time, the dirt precipitates out and lines the bottom of the oil pan. It will sometimes come off in chunks when warmed up the first time the engine is run. If the oil is changed at the end of the season, with the engine run until warm, most of the dirt in the oil will be suspended in the oil, and you will have clean, new oil sitting in the engine that will not deteriorate during storage. 
Brake Hydraulic Fluid should be flushed every 2-3 years depending on the operations and storage environment of the car. If you only drive the car on nice days, and keep it in a relatively climate-controlled garage, you can go toward the longer periods. If the car is driven in bad weather and/or pressure washed often, go toward the shorter periods. Brake fluid, by design, is hygroscopic which means that it absorbs water. This is to prevent water from "pooling" in the system and potentially boiling or causing corrosion. The only way to get the water out of the system is to flush the fluid. 
CAUTION: If brake fluid service is skipped for many years, very often flushing the fluid will cause system failure. It is very important to keep this maintenance current. Refer to the Brake Fluid article for more discussion. 
NOTE: We recommend leaving the parking brake disengaged during storage. In the event that humid conditions occur, this will minimize having the pads stick to the rotors, and, if the cables do freeze up, they will freeze in the un-locked position.
LIFT PISTONS (aka Door Struts, Luggage Compartment Struts, Louvre Struts) 
If it is an option in your storage environment, the Lift Pistons will last much longer in the extended position as the internal pressure is much lower. Carefully weigh this advantage vs. the risk of damage from mice and other animals, children, and environmental dirt. This is probably only a good option in a museum-quality environment. The other option is to remove the struts from the car for the storage season, but this isn't without the normal risk of damage just from doing the installation and removal, and it does make it rather cumbersome to get into the car for any other reason during the storage period. 
Although the DeLorean is covered with so-called "Stainless Steel", we have seen cars with environmental damage to the stainless that shows up in the form of small pits in the metal. These are very difficult to remedy, as the only real option is to grind the outside of the stainless down to the deepest level of the pitting, which compromises the overall thickness of the metal. We see this type of damage on cars stored WITH COVERS in place in environments that are very dirty over long periods of time, mixed with moisture. We also see it on cars store without covers that have build up a thick coating of dirt as well. The moral of the story here is to keep the car clean, and that the cover doesn't really make that much difference over long periods of time. Simply dusting the car from time to time is enough, or wiping it down carefully. It's probably NOT a good idea to bucket wash a stored car, as water will get into areas that don't dry out quickly in storage. 
Another, less obvious, issue with car covers is that often "out of sight" means "out of mind" and after seeing the car in the garage covered for a long time, people start piling other garage items on the car. It may not seem like much but over time it can add up and cause dents in the stainless, cracked louvers, and bent fascias. An exposed car is less likely to have objects put on it. 
Simply air up the tires to the limit shown on the side wall (usually labeled "MAX PRESS 45 PSI" or similar. This will minimize flat spotting of the tires. If you have the space, rolling the car forward and backward even a foot or two on a monthly basis will help with this issue. Lifting the tires off the ground will obviously help too but may cause other issues (See suspension section below). 
There is really nothing special do to with the suspension during storage. Lifting the car off the ground, while reducing pressure on the springs, puts other parts such as the front shock absorber bushings and other suspension bushings under tension that may not be desirable. Springs deteriorate with bouncing and corrosion, not from a constant weight on them. Hanging the car on a frame lift puts tension on the fiberglass body as, in that mode, the weight of the engine and frame is hanging from the body. Overall, leaving the car on the ground, or a 4-post lift that lifts the car by the tires, is probably best. 
Periodically "feed" the seat leather with a good hide treatment. NEVER leave anything on the seats when stored, we've seen where airborne molds can get trapped and actually eat away the seat leather. We've also seen heat from a battery charger shrink the leather. It is best to just empty the car interior. 
This is considered a special case. There are of course times people unavoidably store a car outdoors for a long period of time. This is the worst case scenario for a car, the combination of non-running, sun damage, invasion by animals and insects (and neighbor children) is often fatal to the car. Tires will quickly dry-rot, and anything of plastic or cloth (essentially the whole car other than the stainless) will deteriorate from sun and ozone. Brake discs will rust, brake calipers will freeze up.  If this is completely unavoidable, and finding indoor storage impossible, at least pay attention to the following. 
1 - Use a car cover. This is a contradiction to the above section, but you need to minimize exposure to the sun both to keep the rays off the car and lower the internal temperature. This also keeps rain water from pooling in the top of the engine. 
2 - Remove the cover and clean the car often. 
3 - Cover the tires. Tire covers are available at Recreational Vehicle Supply stores.
4 - Inspect the top of the fuel tank. If the pump cover is compromised replace or cover it. Any rain water coming off the windshield is routed immediately to the fuel pump cover, and if the cover is compromised you will come back to at tank full of water. Water will actually displace the gasoline out of a full tank of gas. 
5 - Put mothballs around the car. Replace often. This will tend to keep mice away but only as long as they are fresh, especially out of doors. 
6 - Park the car on a paved, well-drained surface. Cars parked on dirt will deteriorate very quickly in terms of frame rot and rusted under car parts as they will be wet underneath almost all the time. This may be less of an issue in the arid south, but in humid areas of the world this is a big deal. 
Written DAS 8/14/2016
Revised 1/13/2021 ET (formatting and links)