WS Fiesta fuel consumption calculation

[doctamick]

Many of us have been quoting the average fuel consumption in our WS Fiestas, as calculated by the car’s trip computer (see http://www.fordforums.com.au/showthread.php?t=11263743). Has anybody compared these values with a simple manual calculation (i.e. using the distance travelled and the actual amount of fuel pumped into the tank)??

For the last few tanks of fuel, I have been resetting the odometer and average fuel consumption on the trip computer. My trip computer had been showing me what I thought were awesome fuel consumption figures (5.7 – 6L/100km!), averaged over a full tank, and doing mainly freeway driving. However, after doing the manual calculations, I have been very disappointed to find that the fuel consumption is consistently being under-estimated by about 10-15%!!!

Although 6.5ish L/100km is still pretty good, I wonder if this is a scam by the manufacturer to make us feel like the car is more economical than it really is. Has anybody else experienced this?