Speed sensor replaced now bad mpg

Replacing speed sensors will have 0 affect on gas mileage. Gas mileage will never be the same and will change due to various reasons. The biggest reason is the winter time. Gas stations switch to a winter blend which causes lower gas mileage but is a necessity to prevent the fuel from freezing inside your car during freezing temperatures. Driving habits also affect gas mileage a lot. Make sure your tires are properly inflated at all times. With the constant changing in temperature, air pressure keeps rising and dropping affecting vehicle tire pressures. All this info is based on if you live in an area that actually experiences winter unlike places like florida.