That depends on the Taurus in question and what engine it has, as well as the wheels and even tires. I'm sure you can easily get it up over 100 miles and hour, though. Are you thinking of racing?
The 2006 Taurus is rated 20 MPG by the EPA.
When I say 140MPH on the speedometer I mean it reads 140MPH. I'm not sure if the speedometer is accurate at that speed. I could test it with the GPS but I haven't. I know my bike will do 180MPH according to the speedometer but it was only doing 165MPH or 170MPH.