Who said that these filters were identical?
The P1 is probably a marginally better filter, but in use the difference is of no practical concern.
I've used both and would use either again.
not surprising in the least.
not sure how common knowledge this is, so forgo me the giant DUHH!! if it is,
but last time i checked, The Current Purolator brand is a 50/50 co-venture between Bosch, and Mann-Filter.
They use nearly identical media, AFAIK, and very similar construction aside from gasket here and there and the canister paint. Thats about it. Very close to clones. More like 1st cousins or siblings.
i just happen to have both on hand for the same application... if anyone is willing to send me $10 to cover the cost of the 2 filters, i'd be willing to dissect them and post the results...
i know it's just $10, but it's also $10! I could buy lunch for 2 days w/ that!