So I bought a 2004 Endeavor with 136,000KMs a couple months ago and wow its hard on gas. So doing some research its suppose to burn around 14.5L/100KM in the city and I did a little test. I filled the Endeavor with supreme fuel and drove to my girlfriends which is 102KM away and half of that is highway driving at 100KM/Hour constant. When I got back I filled it again and put 18.33L in the tank. My Endeavor burns 18.33L/102KM not all beings city driving, maybe age is getting to the SUV. I know changing the spark plugs and air filter would help but is there anything else that could be done? Thanks

 

Try a high quality fuel system cleaner. I use Lucas in mine. I have an 07 with 75k miles on it and I get 18-19 mpg city and 24-25 highway

 

I changed the Spark Plugs ,Air Filter and use 92 Octane Fuel, I am not noticing a change. I called Mitsubishi about the Fuel Filter and they dont recommend changing it. I have tried the Lucas injector cleaner thinking it would also help quite my injector tick, the tick is still there.