Your big problem is that although diesels generally give the best mpg (30 per cent more), used diesels of more than three years old are having expensive problems which make the fuel savings look like chickenfeed.

The least problematic seem to be the KIA cee'd 1.6CRDI and Hyundai i30 1.6CRDI (they share the same engine and are essentially the same car). These are chain cam engines, so no £500 belt changes every 40,000 - 60,000 miles. And, up to about mid 2010, they were not fitted with diesel particulate filters (which can cost £1000 about every 80,000 miles).

Another reader went brilliantly off the wall, bought a Peugeot 396 2.0 Coupe, converted it to LPG and is now approaching 190,000 miles.