A new clean fuel reduces wear and tear and improves vehicle’s performance,” AnumitaRoychowdhury, executive director, Research and Advocacy, Centre for Science and Environment (CSE).According to data available with CEEW, there were around 10 million registered vehicles in Delhi in 2017. Of these, one-third (nearly 31 lakh) vehicles were cars and the rest were two-wheelers. However, not all of these vehicles may be plying as there is no system of de-registration once an automobile is scrapped.Studies estimate that in Delhi, vehicles together contribute between 15 per cent-25 per cent to PM2.5 levels.As not many vehicles have compatible engines, a ground-breaking impact would take time. “We may see the benefits once a sizable number of vehicles have transitioned to BS-VI. This will take a couple of years as there is a lag between policy implementation and impact,” said Dholakia, “Studies show that there would be pollution reduction benefits by using BS-VI fuel in cars which have BS-IV engines. The benefit will be around 40per cent-50per cent reduction in pollution for every kilometretravelled.”So far, only Mercedes-Benz and BMW have introduced BS-VI compliant vehicles in India. “Given the policy announcement, I believe other car manufacturers will transition to providing BS-VI vehicles in the near future,” he said.Citing global experience, Roychowdhury said with the current , 8-9 per cent reduction in PM2 and toxic sulphur levels is possible. By 2020, new vehicles would need to have BS-VI complaint engines and this would help achieve the target.So, will Delhi breathe easy in the coming winter? “Slightly,” opined Roychowdhury. “Graded Response Action Plan (GRAP) should take care of the rest. There are several other variables impacting air pollution levels and they would also need significant attention,” she said.The GRAP was prepared by the Central Pollution Control Board last year on directions of the Supreme Court. It enlists several contingencies and long-term measures to be taken to reduce air pollution and toxic components in the environment through a step-wise plan.“Further, we need to complement this through measures that address mobility needs of people. Some measures are a transition to zero-emission electric vehicles, investing in better public transport (on the supply side) as well as congestion fees and zoning (demand-side interventions),” said Dholakia.