Whilst my Aero shows 23 - 26 mpg the speedo is at least 10% optimistic, so is the odometer out too ? In which case it's only doing around 20 mpg??? I must check mileage against the sat nav next time out, any comments?

1969 4/4
1995 plus 8
2002 Aero S1
2013 M3W
2014 Plus 8