while researching a problem for an older buick last week i stumbled upon a tsb(technical service bulletin) from GM about fuel economy from 1994ish. a tsb is one step lower than a recall. i tried to upload the document (pdf) and its way bigger than the 19KB limit(anyone know why its that small). In the tsb it talks about alternator load and it's affect on fuel economy. for every 10 amps of load on the alternator it lowers fuel economy by .4 MPG.