India will switch to the world's cleanest petrol and diesel from April 1 as it leapfrogs straight to Euro-VI emission compliant fuels from Euro-IV grades now. This has been achieved in just three years and not seen in any of the large economies around the globe.India will join the select league of nations using petrol and diesel containing just 10 parts per million of sulphur as it looks to cut vehicular emissions that are said to be one of the reasons for the choking pollution in major cities.State-owned oil refineries spent about 35,000 crore rupees to upgrade plants that could produce ultra-low sulphur fuel.BS-VI has a sulphur content of just 10 ppm and emission standards are as good as CNG.