You should buy a bigger oil filter like I do and I change my oil at 7k miles. The one I buy is for 1990 Mazda 929. It's half longer than stock Protege one.
I went to the Fram website to compare different oil filters (
http://www.fram.com/ )
Theses are the specs for the stock P5 filter: Part Number TG6607
Product Type Tough Guard Lube Filter
Anti-Drain Valve YES
Gasket I.D. 2.27"
Gasket O.D. 2.53"
Gasket Thickness .2"
Gasket Usage Base
Product Height 2.63"
Product I.D. 20mm x 1.5mm Th'd
Product O.D. 2.69"
Relief Valve Setting PSI 13
These are the specs for the 2002 Mazda 626 V6 (in 20003 they switched to the Mazda 6, with a different engine and oil filter) : Part Number HM7317
Product Type High Mileage Oil Filter
Anti-Drain Valve YES
Gasket I.D. 2.22"
Gasket O.D. 2.48"
Gasket Thickness .28"
Gasket Usage Base
Product Height 3.47"
Product I.D. 20mm x 1.5mm Th'd
Product O.D. 2.69"
Relief Valve Setting PSI 13
The 1990 Mazda 929 oil filter has these specs: * * Part Number HM3593A
Product Type High Mileage Oil Filter
Anti-Drain Valve YES
Gasket I.D. 2.13"
Gasket O.D. 2.42"
Gasket Thickness .2"
Gasket Usage Base
Product Height 3.39"
Product I.D. 20mm x 1.5mm Th'd
Product O.D. 3.02"
Relief Valve Setting PSI 12
It looks like the 929 filter is the biggest. I don't think the gasket dimensions matter because the mating surface on the engine has quite a bit of room for a different size gasket. The 929 filter is 1/3" "fatter" than our stock or the 626 filter which may be an issue if the filter is stuck upon removal and you need to use a filter wrench on it. The 929 filter has a blow-by rating of 12 PSI as compared to the 13 PSI of the stock filter which is close enough in my opinion.
The 929 filter appears to be a VERY common filter on earlier vehicles so it should be easy to find at a good price.