2018 Citroën DS - My oil cap disappeared

Not sure if oil cap fell off or blew off while driving how do I know the difference sorry if it sounds stupid

it probably was not tighten all the way and vibrated loose or someone for got to put it back on. if it blew off you have a lot bigger problems.

How to tell the difference ? Put the cap back on , make sure it is secure and if it comes off again you will know that you have a problem .


and check your oil level because you probably lost some.

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Who changed your oil? Odds are whoever did it left it loose or off.

On a 2018 it’s very unlikely to be anything more than a loose cap.

Does this Citroen’s oil cap screw onto the engine, like most (or all… ?) modern oil caps?
If so, then it couldn’t have blown off or even fallen off unless someone failed to tighten it after they put it back in place.
Or, as was already suggested, someone simply forgot to put it back after adding oil.

No experience with the C-DS, but it’s possible the crankcase is becoming over-pressurized b/c of a problem with the pcv system or whatever it is that vents the crankcase. As the engine runs some exhaust gasses get past the rings, that’s normal, and these gasses go into the crankcase (below the pistons in other words). The crankcase venting system (it’s called pcv on most cars) is what removes those gasses from the crankcase. Maybe that’s not working on your car.

Look harder, it could be around somewhere under the hood. Beats paying for a new one.

Not likely in a 2018, plus the dipstick would have blown out long before a properly tightened filler cap.

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