I have used many spark plugs in my 03 Mazda Protege DX.
I was wondering how they worked for you.
Out of all of the bunch I came up with the best as in.
NGK BKR6EK ( Needs better octane 89 - 91 )
NGK ZFR6F-11 ( Needs better octane 89 - 91 )
BOSCH F8DC4 ( NON-Resistor Needs better octane 91+ )...