The internal-combustion engine, says Daedalus, is inherently dirty. A gas explosion or ignition occurs in a cold cylinder, and the molecular combustion chains are quenched on its cold walls. DREADCO engineers are now seeking to make the two-stroke diesel, the dirtiest of them all, into a clean motor.

Daedalus recalls one test diesel engine that could not be turned off because it was burning its own lubricating oil. Old technology used mixed oil and petrol to drive and lubricate a two-stroke engine. So Daedalus's new engine will use the same oil first as lubricant and then as fuel.

A diesel engine is ideal for such experiments because it can burn almost anything. Whereas petrol has to be carefully formulated, the earliest diesel burnt coal dust, and almost any oil will power a diesel somehow. The ideal engine would have a cylinder so thick with oil that all combustion chains would be terminated by a liquid film. The fast-flowing lubricant would be rapidly dirtied, because all the pollution would end up in it. But instead of cleaning the oil, Daedalus wants to burn it.

The key component here is the cooling system. Every diesel engine has to have one — apart from the adiabatic diesel, that is, which just runs hot — and Daedalus proposes one large enough to cool not merely the engine block, but the exhaust gas as well. The engine will then discharge cooled filthy exhaust. Daedalus wants to flow this outgoing exhaust against incoming spent lubricating oil, possibly on a rotating disc or corrugated cylinder. If this is designed properly, the outgoing gas should yield up its nasties to the incoming oil. Carbon, other solid particulates, nitrogen oxides and similar pollutants would be taken up by the spent oil, leaving only clean air (still carrying water vapour and carbon dioxide) to leave the system. The dirty oil will feed the diesel. It will first lubricate, and then drive, the engine.

The new DREADCO engine will have a modest capacity, much less than a litre. Its cooling and auxiliary gear will be heavy, making it more suitable for urban vans than for motor cars. Its cleanliness and use of fuel as lubricant will be a bonus. But Daedalus hopes that the use of incoming fuel as a pollution-scavenger will be more widely adopted by internal-combustion engineers. It should give their engine another boost in its long fight against the encroaching fuel cell.