Is is possible to retrofit the chrome gas cap from F56 to a F55? The F55s have body colored plain gas caps and I like the chrome's look.

 

Should be easy, the cap comes off easily. If I remember correctly there is a little slot on the inside of the door cap that you stick a flat head screwdriver, and then twist off the cover.

 

I guess you have a non-S F55, because the S model comes with a chrome cap.

It's more involved than just replacing the cover. The chrome cap version uses different filler door parts. You have #2 cover along with the greyed filler door in the diagram. You'd have to get parts #1, #3, and #4. The chrome piece is #4. You'll have to paint #3 body color (it only comes primed).

http://www.realoem.com/bmw/enUS/show...diagId=41_2305

 

It's been done many times on the R56 so I'm sure it's possible. The fender sheet metal is identical between the two models (S and nonS).