test driving used cars with the scanguage ii
 

I have a scanguage ii that I use religously.

I want to use it to test drive a few Corollas that I am looking at. Is there a way of configuring it, without filling up, so that I could get (more) accurate instant MPG readings when I am test driving the cars?

I know that I should set the engine size. I do not want to fill up each car's tank and drive around a lot to get more accurate readings. I doubt the current owners would like the idea of that either.