Doing an oil filter change on he R90/6. The filter I got from Rainbow is the 2 piece filter, which in Clymer is shown as the filter for the housing with a single cover. Turns out my housing has a twin cover and (as per Clymer) the filter that I have removed is the single piece version. The 2 piece filter outwardly appears to be the same overall length / diameter - are these parts interchangeable? The 2 piece is part number 11 42 1 337 570, to one removed is 11 42 1 337 572.
