There are 3 holes in the top of the rear bumper. The middle one definitely acts as a drain hole. On my car, the driver's side one is pretty much filled with black plastic but water can drain out. On the near side the hole is entirely blocked with black plastic and water accumulates in the well on the bumper below the rear door. As the car is generally parked sloping towards that side, water often accumulates and I'm concerned about it rusting.

My local Ford garage says that only the central hole is a drain, the other two are just where the plastic outer part of the rear bumper clips to the body. Is this true and if so a deliberate Ford ploy to limit the life of the car?

As a supplementary question, what period is the average fuel consumption calculated on this car's computer?