OK, I'm beginning to think this must be impossible, and I'm gonna feel like an idiot when someone explains it, but I still have the 3 and a half full 2ltr milk bottle with my old engine oil in em, sitting in the garage.
I unscrewed the sump plug on my R32 RB20 (its in an Aus R31 if that matters), drained the oil into a bucket, then poured it into 2ltr milk bottles, filling 3 of them and half filling one. As I've been doing some searching, it seems like 4-4.5 ltrs is the maximum amount you would put into a RB20, but this equates to 7 ltrs.
I'm thinking aftermarket sump maybe? Doesn't look anything special, just black, but I simply can't think of what else is could be. Could the RB20 be overfilled by such a large amount and not crap itself?
Any help would be great as I'm going to be replacing the oil tomorrow and need to know if I need to get another 5ltr bottle...