It is very interesting to compare PSID of synthetic oil filters (Amsoil, Royal Purple, Fram) and semi-synthetic (Mobil-1).
How much is the difference?
1x(=no difference), 2x, 4x?
The best to the worst flowing filter in this graph is only 5 PSI difference at 10 GPM. At 5 GPM, it's only a 1.5 PSI difference from best to worst flowing filter.