Filter Length.
I had the Ford filter and the Fram side by side at the store. The Fram was closer in construction to the Mazda filter (which I used), and the same length. The Ford filter was slightly shorter, and had the plastic 'swiss cheese' tube in its core which the Mazda lacks. It also seemed to have a rough texture to the filter element, and fewer pleats.
After doing the oil change, I have no problem with the cartridge. I find it as easy as any other filter to change. I had liked the Motorcraft sleeve/tube, until I found the Mazda has one attached to the filter cup for the filter to slide onto. So unless Ford had some filter integrity issues I can't see the point in the extra sleeve. As a small bonus, I think the cartridge type filters are probably a little more eco-friendly as there is less to recycle (no metal shell).
The only reason I would go with an aftermarket filter is if it would have a benefit to filtration quality. The Purolator Pur-One filters (available for the 5) have a very high rating, and I have used them in many cars over the years. That said, they are about the same price as a Mazda filter, so unless I see a problem with the OEM, I will probably stick with them. With my 1994 Protege, I was using OEM (stamped 'Made in Japan') filters UNTIL the dealer swithched to a Canadian made filter that looked like a Fram with a blue shell and Mazda painted on it. My Mazda cup style filter wrench no longer fit, the quality was not there, but the price was still $12-14 at Vancouver dealers. At that point I went to Purolator since I would at least get what I paid for.
As far as the K&N drop-in air filters, I have not put one in my 5 yet, but I have in all my previous cars (including my '94 Protege, '97 MX-6, '01 Protege, and my '88 GTX among others). I will not argue about the K&N letting more dirt into the engine, as I have not heard of that before. My 2001 Protege was used for driving instruction, and had 300 000km on the K&N filter with no issues with the motor or the filter itself. I like the re-usable aspect, but I do not feel there is any performance gained. They pay for themselves within a few years, and I never need to keep a spare on hand (although I tend to keep the last used paper filter in the K&N box in case I sell the car
).
- JP.