Should I change my fuel filter before or after I add a special fuel additive?

change it first in case the additive would wash the dirt up into the engine.

Don't expect a real miracle here since most fuel issues actually develop from the AIR INTAKE side of combustion, not the INJECTOR side. THe factory injectors will stay clean as long as you are using a TOP TIER fuel with detergents in it. If you insist upon using a fuel additive, change the filter ffuel to the engine, and the other line sends the unused portion back to the tank. In this way the fuel is CONSTANTLY filtered, over and over again, in this cycle. Your REAL problem will be in dirt on your THROTTLE BODY and in your IDLE AIR CONTROL valve, it's adjunct. THese things get clogged up with oi sludge over time and stop responding to computer signals that fine tune your AIR/FUEL mixture. The IAC is CRUCIAL to oxygen sensor life and in preventing clogging of your converter. Nearly ALL converter clogs and failures are CAUSE by a dirty IAC valve or intake vacuum leak, believe it or NOT!!! Use the SEA FOAM with a NOZZLE< and clean your IAC and t body to SHOWROOM! This will do the MOST good for your engine, power, and economy!!! Follow up with GUMOUT spray. ALl my recent cars have the ORIGINAL exhaust system and converter on them BECAUSE I use synthetic oil, BOSCH fusion plugs, and keep my IAC's CLEAN AS HOSPITAL floors. GOOD LUCK!!

After.

they should take away your license