Your Z4 sounds just like my car in terms of mileage lol. I eventually hope I'll top at least 42 highway realistically, would be cool to get 55 going 55 and be able to really give Prius drivers the finger but that's probably never going to happen.

Almost forgot I was going to buy that stupid sensor today, I just bought a set of 3 1991 Nissan 300ZX wheels (which are really wide compared to my stock wheels) which I fully expect to lower my gas mileage but at least I might not spin tires as much. Money is getting pretty thin, might not have the budget for the sensor after I get done in the junkyard tomorrow.