FYI for those interested - foam pipe insulation costs less than $5 & offers a number of advantages over the covers that Paul makes. Foam insulation is infinitely adjustable in terms how much much grille space is blocked. It is also much more air-tight if you so desire. It also provides better insulation when the car is off.
This is true, but from my testing I saw a 2mpg improvement from the smooth aerodynamic surface at HWY speeds. If you really want to save money just use Packing Tape, it's just as effective as foam and doesn't cost anything. But it doesn't look that great, function over looks.
I just drove to Williams, AZ and back, about 3600mi on I-20/I-22/I-40 and averaged 47.2 MPG with temps from 20*F to 70*F(most of the time 40's to 50's) and strong winds in OK and TX, not ideal conditions for the best FE. BTW I use clear packing tape to tape around the edge of center Grill Cover to seal it off completely, (very aerodynamic) when it is cold. Also I taped up the Top Grill to limit the cold air in ICE compartment and Air Intake before coming back from AZ. I monitor air intake temp on ScanGaugeII and typically it is abut 10*F warmer than outside temps at FWY speeds so best IT(air intake temp for ICE(engine)) is probably in the 90-100*F range, outside temp 80-90*F when we get the best FE. That helped raise up IT by 20-30*F which I think helped my FE by 1 mpg and speeds up heating up the ICE also. I averaged EV% about 43% of the time.
Edited by ptjones, 10 December 2015 - 06:42 PM.