How to Change a KIA Optima Fuel Filter | It Still Runs The fuel filter location varies with engine size on the Kia Optima. The 1.5-, 1.6- and 2.4-liter engines have the fuel filter located under the car in the front left corner of the fuel tank. The 1.8-liter engine has the fuel filter located on the driver’s side firewall. All the filters have the same replacement 2011 Kia Optima Replacement Fuel Filters – CARiD Kia Optima Electric/Gas 2011, Fuel Filter by Genuine®. Fuel Filter and Pump Housing Assembly. If your fuel system parts are in need of repair, don’t compromise the performance and safety of your car with suspect, off-brand replacement..