I just purchased a Toyota Yaris. The official figures for the 1.3L engine give 5.7L/100km for manual and 6.3L/100km for the automatic.

Now in a high-end car with a sequential gearbox this is different, but for a small town car when you'll be doing a lot of starts and stops you'll see the losses on the hydraulic coupling.

That's based on the official figures. No-one gets the listed MPG ratings in real life and automatics suffer worst than manuals for under-shooting the official mpg rating.