Am I the only one that thinks the increased wear on battery and starter would negate some of the savings made from less fuel burnt. Also engines not at running temperature are less efficient and you'd think stop start would barely allow the car to warm up on short journeys. The combination of this and the fair bit of fuel used to start the engine would seem to almost completely negate the savings. That is unless you're stopped for quite a while in which case you could shut off the motor yourself, I've done this a few times in bad traffic.