tcuallstar

my Self diagnostics has been throwing a Dtc5284 for a while now, my stang doesnt drive any differently, but my gas mialage has been starting to suck recently. i the last time i changed my oil was with royal purple, and im not due for an oil change untill 19,000. im at like 17,000 right now. the question is, could this have anything to do with this code? i showed the ford dealerships technicians and they tried to tell me the self diagnostics system wasnt stock and that i had put it on there aftermarket.