Wanted to see if installing vortec generators on the roof, trunk and front fender would improve FE. Did 4 runs on a 7.5 mile north south section of highway with cruise control set at 60. Did runs with a clean car, with VG on roof, VG on roof, trunk, and front fenders. Temperature was 93 and winds were out of the south at 15mph. VG's were made from hand out of aluminium.
#1N #2S #3N #4S
Clean car 42.0 38.4 42.1 39.0 AVG 40.38
VG on roof 42.6 39.2 42.8 39.1 AVG 40.93
VG/roof/trunk/ff 42.9 39.1 42.9 39.0 AVG 40.98
That's only a 1.5% increase in FE and it looks like the VG anywhere but the roof are ineffective.
On the front wheel well