R11 is 2.3 eng. [230sl]
2.5 eng. is R18 series [250sl]
These are both Independent oil resevoir/dip stick pumps.

2.8 eng use pumps starting with R20 thru R 24 series .
The main change from the earlier resevoir pumps is these pumps no longer have res. and are force feed lubed from engine crancase oil sytem.....different pumps