Gasoline Discussion

General:
The DeLorean fuel tank holds a little over 13 gallons-51.6 liters exactly. 
 
The engine's static compression ratio is 8.8:1, so 87 octane  (US spec (R+M)/2 > 87) regular gasoline is sufficient for all stock DeLoreans. 
 
We recommend the use of name brand "Top Tier" fuels if available in your area.
 
However - DeLorean Motor Company recommends premium grade fuel under the following conditions:
  • Modified Engine/Timing - Engines equipped with the DeLorean Motor Company Stage 2 Upgrade. Part of this modification involves running more cam opening and more ignition advance. Premium fuel is required to avoid compression detonation.
  • Modified Engine/Boosted - Turbo or Super Charger installations. Due to increased cylinder pressures, Premium fuel is required to avoid compression detonation.
  • Long Term Storage Vehicles - Premium fuel will generally "last" longer in storage. See also the article on Long Term DeLorean Storage. The use of premium fuel will cause no harm to the system.
Oxygenated Fuels ("Ethanol"):
The presence of ethanol in concentrations of 10% or less can be tolerated by the fuel system without difficulty under normal operation. Long term storage (over 90 days) of cars with ethanol fuels can cause issues. If you know the car is to be stored for longer periods of time, we highly recommend adding a fuel system stabilizer (Sea Foam, Sta-Bil, etc.), then running the engine to circulate the preservative, AND then draining the fuel system. If you have the option in your area of using "real" gas, i.e. without added ethanol, we highly recommend you use it.
 
Gasoline Shelf Life:
Gasoline today has a "tank life" of not more than four to six weeks. As the fuel begins to degrade, the following effects will occur:
  • Hard Starting when cold. If the car seems uncharacteristically hard to start when cold, the fuel may have started to "turn bad". If you note this, try to use up the remaining fuel in the tank and then add fresh gasoline to the tank - and drive it some more. Even better, drain the tank (it will still run your lawnmower just fine) and replace the fuel.
  • Failure to start. Eventually old fuel will not run the engine. At this point the fuel will likely have a "paint thinner/turpentine" smell to it, and won't really smell like gasoline any more. In this case it is imperative that the tank be drained, the system flushed all the way through the injectors, and fuel replaced. Leaving bad gas in the vehicle for long periods of time can lead to replacement of the entire fuel system.
  • Contamination. At this point the rubber parts in the system have dissolved, and the fuel has turned gummy, which can freeze the fuel pump, freeze the fuel distributor plunger, plug the warmup regulator, plug injectors, and freeze the frequency valve. Contamination can also consist of water introduced into the system via a failed fuel pump cover.
If storing a car for longer that 90 days, siphon all the fuel from the tank to guard against deterioration to the components in the tank.
 
Draining the system provides two benefits:
  • Avoids deterioration of in-tank rubber parts. NOTE replacing the in-tank components with the Fuel Pump/Sender Module P/N 107000, eliminates the rubber and mild steel components in the tank that often deteriorate and cause fuel tank contamination issues.
  • Allows room for the introduction of fresh fuel when you go to restart the car.

By Warren Wallingford with edits by James Espey, DMC (Texas)
Revised 6/15/2016 DAS [edits/elaborations]

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