As with any engine, one of the keys to long life is regular oil changes and the DeLorean is no exception.
Except in extreme climates, we recommend conventional Castrol 20W50 motor oil, and specifically DO NOT recommend the use of any synthetic oils in the PRV engine.
Oil should be changed, with a new filter and sealing washer every 3,000 miles or a minimum of once a year. If you are on a once-a-year schedule, it is best to change the oil in the fall (before the long winter "nap") to remove the old oil and the solids that it contains. This will avoid having the solids settling to the bottom of the pan over the storage period, and removes stray moisture and acids from the engine.
The oil filter P/N 102114B is a spin-on type with an anti-drainback valve. The ones we sell are made by Bosch. The original equipment Purflux-branded filter is no longer available in the US.
The drain plug is in the front of the cast aluminum sump. The drain plug has a somewhat rare 8MM square that requires a special socket P/N 111104 to remove. Every time the plug is removed, the crushable washer behind it must be changed. Failure to do this will allow oil to leak from the drain. Every time. This crush washer P/N 102101 is included with the filter that we sell.
The specified oil capacity of a DeLorean engine, including filter, is approximately 6.75 quarts (6.4 liters), but in reality it takes a bit more to be at a good level on the dipstick. The best way to fill the engine is to install 7 quarts of oil. Then run the engine for a few minutes, turn it off, and recheck the oil level after a minute or so to allow it to drain back into the sump. Generally 7 quarts will put it in the mid-range (between the two marks) and 7.5 will get it to the top mark.
Written by Warren Wallingford, DeLorean Motor Company (Texas)
Updated 6/6/2016 DAS [details, links]
Updated 9/15/2016 revised fill recommendation.