i agree somewhat with the "use oem filters" statement in some applications. just to make up #'s here, but lets say there are 50 fords to evey 1 subaru on the road, so in the ford case i would use/assume an aftermarket filter will be speced the same, but in the subaru case, i wouldnt just assume that. i would do some research and make sure its up to oem specs. aftermarket suppliers will say a filter is the same, simply based on dimensions/fit, not filtering specs etc. just as some will buy a filter made by an aftermarket supplier based on the fact that the aftermarket supplier also made the oem filter. that does not automatically make it the exact same filter. think of this, when i go to napa and ask who makes their napa branded oil, they reply "its the same as valvoline", when infact, its bottled by ashland as is valvoline, yet it is different than valvioline in reality. as with my world (OPE), ive seen hydralic filters said to be direct cross' by aftermarket makers and when put to use, the mowers not even move, because the oem didnt have an adbv but the aftermarket did, or vise versa.