I got 22 MPG the other week. Straight piped and intake is all that's done. Pretty much did 55 for the 220 miles I did in those 3 days. Haven't gotten that since :/ mainly due to fuel leak.
C2500. 4.10's. RCLB.
In all honesty...I don't think the fuel heater is really needed, even in a place like Boston. The diesel gets additives in the colder months to keep from gelling. Although diesel does burn better when its warm.