Tom-stopping the motor can save some fuel. My Scanguage tells me
1)Small 4 cyl about .2 gal.hr at idle- 2001 Prizm(corolla) 1.8 4cyl
2)Decent sized V-6 .4 GAL/HR Honda Pilot
3)V-8 ,5-.6 GAL/HR Nissan Titan 5.6 V-8
The Prius seems to use in the .2 gal/hr range.I suspect it uses less, but the scanguage only reads to 1/10th gallons.
Lots of folks spend an hour a week idling-a V-8 will save 180 gallons($500+) a year if it had a shut down(ignoring AC etc). Luck,Charlie