I know this is a simple thing but;

 

I was checking my gas and filling up my oil (front seal leak) and as I was tightening my oil fill cap I noticed it just kind of rattled when twisted on hmmmm... (remembering others earlier post on how these engines build negative pressure and these caps must seal) I noticed the gasket in the oil cap was hard/brittle and very thin and was not sealing.

 

so I found some rubber gasket material, cut a new one and now nice and tight. (I will call local dealer and see if original can be had.)

 

Still learning and appreciate all the great posts.

you can also bend down the locking tabs

 

I have one with the return oil line that is so tight it takes a wrench to turn

The one the dealership is likely to offer will be the wrong cap. The part number supercedes to another part, which is a screw-on style oil cap, which, of course, won't work on an EA82.

but the one for a ea71 will

 

if you need one, it's yours

A while back I suddenly was getting an exhaust smell at idle whenever the climate controls were on anything but A/C max. It went away when I tightened the cap. I expect exhaust gases from the crankcase were getting into the A/C intake.

Plus, if your valve guides/seals are maybe just the teensiest bit worn , keeping the oil cap tight helps a lot. You know, on those OTHER vehicles where you pour the oil in over the rockers and hope it seeps down to the crankcase eventually.

You can get a Stant replacement cap at any auto parts store for about $3.