I get 24 MPG if I drive like a grama or beat the hell out of it. City and highway are the same. With that unplugged your mileage might drop. Idk how that part works yet (it's taking 3 years to get to this point and mostly without forums), but from the many docs I've seen it controls timing on certain models and second it controls fuel enrichment metering to atmosphere temp. Don't know for sure but its a reverse metering gauge with the same values as the water temp sensor. I tried sticking mine outside the engine bay, attaching it to the AC drier but my MPG and power fell on its face. Its a possibility so maybe someone with more knowledge of the sensor will chime in. I actually hope they do cause I wanna run a solid value if possible. How old is your water temp sensor?