Ok listen to this... I bought my HX civic used. Now that I have it I dont know what has been replaced or if the 60k service was done. Im 16 so it takes me a while go earn money to buy shit like rims and expensive stuff. So I figured that I would start replacing stuff that I know wont cost much to replace and so on. Well I read this tread about spark plugs are saw the mixed reviews of the Bosch Platinum and NGK plugs. So yesterday i decided to go to my local autoparts store and get some NGK plugs. I get them and drive home happy. I read the thread alittle more and notice i have the plugs for a EX civic insted of HX with takes a different one i guess becouse it runs super lean. (And i noticed this thanks to Duce Black Coupe cuz we both have HX's(thanks man) Any way I take them back and ask for the right plugs. Of couse they dont carry the right NGK plugs. So I give in and buy the Bosch plugs. Can those plugs have hurt my motor? Would they have any affect on performace or gas mileage? By the way.. they where NGK and the differnce in the part # was they were a 5 and the HX takes a 4... Thanks 