Automakers, long the target of anti-pollution rules, have taken sides with their former environmentalist foes to urge reforms on a different industry: Oil refining. The goal, as it has been for decades, is cleaner air, and this time the Environmental Protection Agency is going to the source - petrol makers. The EPA wants a ten-fold reduction in average sulphur content in motor fuel by 2004, something the refiners say would cost them billions to achieve.Environmentalists targeted sulphur because it is a component of acid rain. Automakers, who were forced by the Government to retool cars to improve fuel mileage and reduce emissions, want less sulphur becaue it keeps automotive catalytic converters from efficiently reducing the hydrocarbons, nitrous oxides and carbon monoxide that cars emit.