I have a Jaguar S type 2004. I have noticed lately that the Milage Range on the speedo goes down quicker than the car mileage goes up. so if my range says 300 miles and my speedo says 91,000 miles by the time the Range has gone down to say 150 my speedo mileage should have gone up 150 miles but it might have only gone up 140 miles. Anybody got or had that problem?

 

Are you referring to the number of miles listed as left on the tank of gas?
If so, then the relationship between that and the actual mileage is only suggestive and is based on prior conditions.

If is it something else, then we need more information.
=================================
My karma just ran over your dogma
Current Hers: '13 Lexus ES350
Current Mine: '08 Jaguar S-Type 4.2 "Satin Edition" (250.06 whp / 259.67 torque)

 

I am in the UK does that make a difference?

 

This is my Speedometer

 

It's a computer. It doesn't know how you'll actually drive so it guesses. In your case you look to be using more fuel than it guesses so stop-go or short trips or heavy foot or ....