KEN W. PURDY is widely known for his writintjs on motoring subjects. His book KINGS OF THE ROAD is a standard work on the great automobiles of bygone days.

A friend of mine bought a new automobile recently. It came equipped with numerous useful accessories, and one not so useful — it has a built-in problem of conscience.

The car is a Mercedes-Benz 190D. The “D” is significant, for it denotes the presence of a diesel engine, and it is the diesel engine that has upset the proud new owner. His home is heated by an oil-fired furnace, and every time he thinks of the 300-odd gallons of fuel oil resting in his cellar tank, temptation smites him, and an angel-versus-devil debate rages within him. For a Mercedes 190D will run just as well on furnace oil at ten cents or so a gallon as on diesel oil at twenty-six cents.

A diesel-engined automobile knows nothing of the snobbery of its gasoline-burning fellows. Not for the Dcar are the golden or purple or pink gasolines drawn from their gaudy pumps at up to forty cents a gallon. A D-car doesn’t care if men of distinction use only Scarlet Pimpernel Petrol. A D-car takes smelly fuel oil and burns it without so much as the help of a spark plug, simply by compressing it so tightly that the generated heat sets it off. It is not true that a diesel engine will burn drawn butter or melted candle ends, but it is remarkably unfussy, just the same. And so the temptation to drain a bucket or two at the oil-burner tank, rather than hunt up a filling station that displays a sign “Diesel" or “Trucks,” is strong. After all, sixteen cents a gallon is — well, sixteen cents a gallon. And when the fact that a 190D will run thirty-five miles on a gallon is thrown into the equation, I suspect the devil often wins.

The diesel-engined automobile is, comparatively, a newcomer in this country, although Mercedes-Benz put the first one on the market in 1949. The highways are full of diesel trucks, but diesel passenger cars are still uncommon — so uncommon, in fact, that the various states haven’t got around to setting up measures to defeat the owner whose cupidity overcomes him. The governor of one New England state did personally telephone the first Mercedes-Benz diesel owner in the municipality to ask him to state where he proposed to buy his fuel, and officials of another commonwealth for a time considered making diesel owners sign an undertaking, under penalty of peine forte et dure, not to run it on furnace-oil siphonings. The project was finally abandoned, however, apparently on the ground that it might well have the effect of informing people of a good thing who might otherwise never know about it.

Adequate law is already on the books, of course, since the use of furnace oil instead of fuel oil constitutes tax evasion. But strict universal enforcement would be a tricky business. A Mercedes-Benz 190D looks very much like a MercedesBenz 190 gasoline burner. It sounds a bit different, if one gets close enough, and its exhaust has the characteristic diesel pungency (it produces fewer harmful contaminants, by the way). And one can, by looking narrowly, see the small chromium “D.” But a snooping enforcer armed with police powers could not make a case by siphoning something out of the tank: the two oils look the same, Ultimately, I suppose, if enough diesels appear on the roads, diesel fuels will be colored, and presence of white fuel in one’s tank will constitute prima-facie evidence of malfeasance. Until that time, diesel owners will wrestle with their consciences — sometimes winning, sometimes losing.