It's a great little nugget of knowledge to have if you've let your
battery age to the point where it just barely starts you up. You can
get one or two more starts by knowing to keep it off during the crank.
Worked for me at a time of great need!

wrote:
I was told the same thing from a UPS pilot friend of mine. While the
current draw to energize the alternator field is minimal it could make
a difference on a cold day(?) Just don't forget to hit the ALT switch
after engine start and verify the draw on the amp gauge.