I should have posted this years ago, but I didn't think about it at the time.
In May, 2015, I installed an under-drive crankshaft pulley on my Mustang. Under-drive pulleys are an old hot-rodding trick to get more power to the wheels by wasting less power driving accessories. (water pump, power steering pump, a/c compressor if you use a/c). Alternator is a wash; the regulator will just increase field current to compensate for the reduced RPM and increase torque required to generate the current required.
I thought this could also be an EcoModder trick, as well...
This is a 25% under-drive pulley. It was about a $279 experiment.
Before I installed the pulley, I was getting mostly 31's in warmer weather. I got occasional 32's, but they were "one in a row".
After I installed this pulley, I had 8 consecutive fill-ups over 32 MPG. Last Summer, I had 4 consecutive fill-ups over 33 MPG.
This will pay for itself in fuel savings in about 150K miles
, but in the mean time, it's giving me bragging rights.