Suggestions welcomed, noticed in the last few months poor gas mileage. Had jeep since 43,000 kilometers and traveled highways and occasional off roads to get to camping areas. Jeep has about 254,000 klm. City would get about 420 klm to a fill-up, now getting 320 per fill-up city.

 

When was last time it got new plugs/tune-up, air filter? Might consider fuel injector cleaner or seafoam treatment.
Any codes?

 

Even a perfectly tuned motor will get less/lower fuel economy during cold winter months vs warm summer months. Gasoline is blended differently at the refinery, winter vs summer, and the motor takes longer to warm up, winter vs summer, so in cold weather, the motor runs in it's Factory programmed "richer" mode longer in winter than summer.