Driving 1500 Miles without oil Filler Cap


Howdy. I have a 2003 Ford Crown Vic. About 1500 miles ago I had oil change and inspection done at shop that has done service and tire work before. Generally very good and helpful folks.

Last night I popped open the hood to check something with the battery and discovered the oil fil cap setting there … on top of the battery … lo these 1500 miles.

This morning I checked and the oil level is fine and there doesn’t look to be any great mess. The fill cap on this engine has a bit of a neck to it so that it is raised up somewhat more than what others might be.

Just wondering … how much a chance is that this experience has screwed up something and will lead to doom, disaster, tsunami or other such vehicular catastrophe …


How much chance? Just about ZERO.

Put the cap back on the filler tube, clean up any oil that splashed out, and forget about it.


A harmless mistake.

Rejoice that you found that cap.


None. The system works by drawing oil up from the oil pool in the pan at the bottom of the engine and pumping it to various locations needing lubrication. The area under the valvecover is just an open chamber where oil drains back through return channels to the oil pan. It’s also sort of a collector for crankcase vapors from which they’re drawn back in through the PCV valve to be burned. While leaving the cap off may have allowed some unburned hydrocarbons to be released into the atmosphere, it did no harm to your engine.

In the old days, the '60s and prior, valvecovers were vented to the outside air through the refill cap. You’ve simply relived the past.

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