good morning my name is XXXXX XXXXX I will assist you today
there are a lot of factors that determine fuel mileage. Adding a chip is performance, not economy.
Tires, make sure they are in good condition and the alignment, which is critical, is correct.
services, make sure all services are up to date. oil, transmission, brake and coolant fluids are all changed. make sure the injectors are professionally cleaned. additives have little or no effect at all.
and most of all, driving habits. no flooring it from stop lights, sticking to speed limits, and just overall good driving. you will meet or exceed the ratings if you do these.