The extensive adulteration of diesel fuel is the major obstacle to the lifting of restrictions on diesel-powered automobiles, a university professor said yesterday. Only trucks, tractors and taxis among road vehicles are allowed to use diesel fuel, according to old anti-pollution regulations. Stamos Stournas, a professor of fuel technology at the National Technical University of Athens (NTUA), told reporters that new advances in diesel engines had made them less polluting than gasoline-powered engines. The new diesel engines allowed diesel fuel with very low levels of sulfur (50 parts per million) to be used. By contrast, heating oil, on which there are no Europe-wide standards, contains 2,000 sulfur parts per million. Stournas presented the results of studies conducted jointly by the Ministry of Transport, the Association of Oil Products Trading Companies and the NTUA. A study conducted in 2002 by the NTUA on behalf of the traders’ association showed that 8.2 percent of the gasoline stations in Attica sold adulterated gasoline and 15.9 percent sold adulterated diesel. In 2003/4, NTUA conducted another survey, this time on cheaper gas stations. This study found 7.1 percent of the gasoline samples and 11.7 percent of diesel samples to be adulterated. Adulteration is the result of the fact that heating oil is very lightly taxed, if at all, and costs much less than diesel. Fuel for ships is also tax-free. The state has several times tried to crackdown on traders of adulterated fuel, with mixed results. Even the mandatory coloring (pink) of heating oil has failed to stem the illicit trade. And should the state allow diesel-powered automobiles to be imported, car dealers would be unwilling to import them, due to fears that the use of adulterated fuel would damage the cars’ engines before the guarantee period expired, saddling them with extra costs. Oil trading company Elinoil said yesterday that its fuel quality control program, adopted since 1998, resulted in nearly eliminating adulterated fuel from its distribution network.