[Tambohamilton]

Please can someone explain what 'nonexchangeable retrospectively', 'exchangeable retrospectively', and 'bilaterally exchangeable' (and any other similar terms) mean on realoem.com? I find them so confusing!

Thanks

[Tambohamilton]

Here's an example:
https://www.realoem.com/bmw/enUS/par...&q=61610427668

Realoem is recommending #427668, but that part was superseded by #159627 (nonexchangeable retrospectively), then #455435 (bilaterally exchangeable).

So I'm assuming that #159627 is not compatible with my car, since the car didn't come with them from the factory. But it looks like #455435 should fit fine? But if that's the case, how does 'bilaterally exchangeable' differ from 'exchangeable retrospectively', in practical terms?

[Efthreeoh]

Bilateral is just a fancy word for "both ways", so to me the terms "bilaterally exchangeable" and "exchangeable retrospectively" mean the same thing.

I'm stumped on an example of "nonexchangeable retrospectively". The only scenario I could think of is say if BMW changed the design of the OFH. You could bolt on a new-design oil filter housing and the old design's oil filter element would not fit the new OFH design.

[Tambohamilton]

That's basically what I figured, but surely there must be a difference between bilaterally and retrospectively...otherwise why have 2 different terms? Seems strange, but then so is the terminology!

That's also basically what I thought about nonexchangeable; the part would fit, but is incompatible with other parts around it.