Following from this post, the trip to Scarborough and back saw 57mpg out of the Fabia, on Tesco fuel. This is with a reduction in speed: 50-55 mph on single-carriageway A roads, 75-80 on motorways (indicated speeds, and mpg from fuel computer, so probably both a little optimistic).

It did show that the oft-quoted fallacy of ’56 mph is most economical’ really is a fallacy: during the 75-80 sections, the average mpg rose. At one time, cars were often tuned to be economical at the 56mph point, because of the steady 56mph test speed. In actual fact, it will vary according to aerodynamics, gearing, and power delivery.

It also shows that heavy traffic and booting it gives a drastic increase in fuel consumption: One recent commute saw 39mpg….