Car Company Deception

I am filling gaps in on my blip journal. I type Saturday 16 September and curiously this image has gained some more significance since the VW scandal has unfolded.
Some folk may think this is just good housekeeping, prudence if you like or just plain OCD. I refer to my habit of always booking my mileage, total cost, cost per litre at the filling station when refueling. With the corresponding data from the previous fill (and the one before that) it is always possible to calculate actual miles per gallon and fuel cost per mile  to run the vehicle. By filling to the top each time and running about 450 miles to the next refuel the anomalies in the calculation caused by variations in precise top up level are generally minimised.

If you are still reading you are probably hoping there is a point to all this. 

My car, necessary for work, is unashamedly a gas guzzling Chelsea tractor, a British made four by four. Among its many gizmos a flick of a button at refuel time allows a reset of the trip computer. In the ensuing miles, on scrolling through it will reveal distance elapsed since last reset, average speed, and critically for me the miles per gallon figure.

If you look carefully in my image you can see that two thirds of the way through a tankful of diesel I am sitting at an acceptable 38.3 mpg. This is a car weighing almost 3 tonnes with a permanent four wheel drive train and a 3 litre 6 cylinder engine. If you honestly believe the figure on display you are bonkers. When next filled up the actual MPG was just over thirty. When it displays 35 actual is 28 or 29 and when it displays 29 (say after a period in urban situation or on slow rural lanes) you just really don't want to know.
This is not my first Discovery. This one and all the preceding models have displayed the same "optimistic" trait with the displayed fuel consumption. The error cannot be explained by variation in top up level as there would be some "swings and roundabouts" trend to successive figures. Plain and simple they are conning the customer by deliberately engineering an error in to the computer figure; possibly massaging the egos of some buyers who would rather not know the reality.

One other bit of irony; my first car to have this type of device fitted was a 1988 model (I didn't have it from new) VW Golf. When I think about it I have been monitoring my MPG for a long time now. I did precisely the same logging of fuel data back then and compared it with the car's reported figure. It was consistently precise and corroborated my own calculation every time. It could be done by VW in 1988 but the same technology is beyond LR  almost three decades later.