I've just spent the day driving the new Land Rover Freelander equipped with stop-start engine technology.
We drove through London traffic to Battersea, where we took the Freelander through its paces on an off-road course inside the old power station.
It negotiated the usual mixture of gravel, sand, slopes, descents, ramps and potholes with the ease that you'd expect from any car from the Land Rover brand but - much more impressively - also achieved around 47-48mpg on the drive into town from Heathrow, where we started our day.
Land Rover's set-up lacks the integrated starter-generator of, say, BMW's EfficientDynamics, but its slightly lower spec system delivers 90 per cent of the benefits at a fraction of the cost, meaning that stop-start is to be fitted as standard to all diesel Freelanders from now on.
I got in to the car thinking, "Hey, what's different? If I want to turn the engine off at the lights then can't I just do that anyway?" But of course, you forget that in the standard car, the sound system stops when the engine cranks, the air-con stops when the engine is off, the lights dim, the braking power disappears on slopes... the list is endless.