The battlelines have been firmly drawn. Auto manufactueres and environmentalists are bracing themselves for September 17 when the hearing on the use of diesel as a fuel comes up before the Supreme Court for the second time. While the Automobile Manufacturers' Association's (AIAM) argument is that diesel is the fuel of the future, environmentalists say that suspended particular matter (SPM, the toxic element discharged when diesel is used) is, to put it mildly, a harmful byproduct.