From Ian Smith, Chipping Norton, Oxfordshire, UK
Guy Cox isn’t comparing apples with apples when it comes to the fuel efficiency of his diesel SUV. Diesel engines are inherently more thermodynamically efficient than petrol engines because the compression ratio is much higher, plus his old, original Minis would have used inefficient carburettors rather than modern fuel injection. Thus it’s hardly surprising that his diesel SUV is more fuel efficient than an ancient Mini. Compare a modern SUV with a smaller, modern diesel hatchback, and the picture would look rather different (Letters, 27 December 2025).
