We don't have mpg as such but we have fuel flow per engine/hr and in total plus total fuel on board/used and also fuel pages that we can pull up which shows the total fuel remaining in each tank.
With the current price of fuel it is in everyones interests to conserve as much of it as possible. Things like flying clean (ie: no flaps out) around the holds and delaying the extension of gear and landing flaps till as late as possible in the approach all helps. In the event of a go around having as much fuel on board as possible will obviously be of benefit in shooting further approaches and avoiding a diversion.
Some aircraft/airlines will be tankering fuel in order to reduce turn around times and to avoid uploading "expensive" fuel at a destination so having enough to get you home plus reserves becomes a factor.