WWLRF do?
#25
Not to turn this into a MPG thread, but my results are due to an electric fan and all new rotating assembly in the form of a top hat liner engine (not why I got it, but a nice side effect). They each netted me about +1 MPG each from stock but one cost $200 and the other $6K respectively. I realize 15.6 is still a long ways from stellar, but it helps.