I am guessing some of it also comes down to nerves, or how far the driver wants to push it. Also if you can get off the mark first because the other wasn't expecting it, it goes a long way.
I raced a Mondeo ST220 whilst test driving a Audi A3 2.0TDi (140) up to about 100mph he couldn't shake me. But then again I was pushing him and was in the right gear to go, so as soon as he started to go I was already accelerating hard, he had to drop a cog or two and then build up so my velocity was already increasing, hsi wasn't. But once we hit a ton I thought that will do, so popped it into 6th and plodded around at probably 40+mpg, whereas he was seeing soemwhere like 20mpg I guess ;-)
Cheers H
Eh....172 Cup vs Focus ST?