The most surprising thing about our recent visit Gordon Murray’s Guildford design emporium, to view a new, Shell-backed revision of the T25 city car, was seeing the sheer scale of the efficiency improvements that have been liberated from the car.

When I first heard that the T25 concept was being “re-thought” with lots of help from Shell and a world-famous engine designer, Geo Technology, I have to say I wondered how much difference even these big-name experts could make, given that the car had been built from scratch by one of the world’s most accomplished designers to be ultra-light and ultra-efficient.

Furthermore, it had already proved itself to be massively more frugal than other road-going production cars in tests backed by Imperial College and the RAC.

Usually, if you want to generate headlines by making something better, it’s best to start with a product that isn’t very good in the first place. Yet Shell’s lubricant experts, Geo’s engine men and Murray’s own engineers have produced a remarkable cut in kerb weight (down by 12%), a big reduction in aerodynamic drag and impressive improvements in engine efficiency.  

Full results are still being assessed, but it’s already clear that the Shell car undercuts the previous T25's fuel mileage figures by a remarkable 8% in the warm-up phase, and 5% when operating normally. In a car-design environment where technical people count improvements in 10ths of percentages, these are big numbers. What is more, early tests on real roads show the Shell car can turn 107mpg when cruising at 45mph, the sort of result once reserved for a sub-100cc four-stroke moped.