Fuel duels - Other alternatives

As used in: Ford F-250, Mazda 5 Hydrogen RE Hybrid, BMW 7 Series; British Steam Car Challenge.

What is it?: Some manufacturers are developing conventional engines that run on hydrogen rather than petrol. One is even developing a steam-powered car.

Where can I buy it? Nowhere in the UK, although BMW has opened a hydrogen filling station in Munich, Germany.

Pros: Low emissions and, in theory, a steam car can run on any fuel

Cons: The main problems are with producing hydrogen and the fact there is no supply infrastructure.

Expert view: Problems remain over hydrogen (see 'Fuel cells').

Outlook: Whether it's used in a fuel cell or internal combustion engine, hydrogen will become increasingly important – but not in the immediate future.