I have a 2001 Mercedes C320 and need to add 1 quart of oil. The oil filler cap that I found is made of plastic and I cannot figure out how to open it. Tried turning, tried prying and have given up. Cannot call dealer until tomorrow.

Any suggestions?

I received the info. The cap had been installed improperly and that is why I was having a bad time. Finally figured it all out and was able to remove
the cap and add oil. 1/4 turn is all it takes.