I've got a strange problem. Ever since I had my battery cables and battery replaced my MPG has decreased significantly. This may just be a coincidence as I don't know how the 2 can be related but I'm wondering if anyone has any ideas about this. For reference in the summer I was steady clocking in at 24.3 MPG and now with the same driving it has dipped down to 19.1. Appreciate any help.

 

On many late models today, whenever a battery has been replaced , the electrical system (charging) needs to be notified of the change. This requires a capable scan tool..
A new battery can be destroyed if the charging syst functions with the info from the old battery still in the system. Some places that sell batteries can tell you if your vehicle will require this update. There may be another reason for the battery going dead and this needs to be checked out or the problem will not go away.