Lower electric resistance MAY help mileage
It might help. My first exotic car was a mid-60s Italian car. It made a loud sound under the hood when the headlights and rear window defroster were turned on. I traced it to a slipping fan belt from the additional load put on the generator. I replaced the wires going to the rear window defroster, got a new fan belt, and adjusted the tension. There were too many changes to know the separate effects, but the noise went away and mileage improved. The bottom line is that generator load can have an effect, especially on smaller engined cars.