[Curly1]

I think underdrive pulleys should be added to the list of 60 things to do to improve effeciency.
I have not done and tested it yet but it appears to me that it will mean the alternator, water pump, air conditioner, power steering and anything ran off of the crank pulley to use less energy. The factory on many new cars is already doing some of these things but they still have a more powerful alternator, water pump, air conditioner etc to allow for worst case scenario. So I think most could get away with underdrive pulleys.
That is a trick I used on my drag race car that should help to increase the effeciency and mileage.
Eliminate all sources of horsepower (mileage) robbing parasitic drag and decrease the amount of drag they have on the ones you have to keep.
On my drag car I completly removed the factory water pump and fabricated a small electric water pump. I also found the smallest radiator and used smaller diameter water hoses cutting about 60 lbs off of the front wheels. Got rid of the power steering and manual fuel pump and put a underdrive crank pulley AND alternator pulley. Then I used two batteries and charged them between races.
Some have done a alternator delete on your cars. I think you need one to run the lights at night and creature comforts. A underdrive pulley system should allow you to have your cake and eat it to.
In many ways drag racers and other forms of racing do the same thing we are. Trying to get the most out of the car by eliminating the things not absolutly required and reducing the drag of the ones that are required.