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BS6 V/S BS4 Norms



The Indian auto industry is set to undergo a significant makeover come April 2020. The Indian government has issued an ultimatum to all the two and four-wheeler makers, which states that only BS6 vehicles can be sold and registered post 31 March 2020. The Bharat Stage (BS) norms, which are an implication of the European emission standards, were initially rolled out in 2000. In 2016, the government decided to forgo BS5 in favour of establishing a stricter standard to track elevated emissions from car exhausts. So here we are to answer all your doubts regarding all the BS6 v/s BS4 norms.

What Are the Changes from BS4 to BS6?

A few of the significant differences between BS6 v/s BS4 norms is that the latter contains five times lesser sulphur content (10 parts per million) relative to BS4 (50 ppm). The aim is to make the petrol-powered vehicles to be 25 % cleaner by reducing the NOx (Nitrogen Oxide) content from 80mg/km to 60mg/km. The case of diesel-powered isn't this straight forward as they have to reduce three aspects of the combustion. For diesel engines, the BS6 norms aim at reducing three pollutants - HC (Hydrocarbons) + NOx, PM (Particulate Matter) and NOx reduction by 43, 68 and 82 per cent respectively. Another significant change to comply with the new BS6 norms will be the presence of OBD (Onboard Diagnostics) and RDE (Real Driving Emission) on all vehicles. After the implication of OBD and RDE, it would help in enabling real-time tracking of emissions. Diesel motors will include DPF (Diesel Particulate Filter) and SCR (Selective Catalytic Reduction) technologies. 

How Will It Affect The Consumers?

The customers are going to have to bear with this transition phase to help control the environmental threat looming at large on us. For the people driving the BS4 or older variants of vehicles can opt for BS6 fuel at filling stations. With the BS6 coming with reduced sulphur content, it means that the emission level would come down to a much lower level. Studies suggest that a diesel vehicle equipped with BS4 operating on BS6 fuel can reduce PM pollution by half. On the other hand, the lowering in the sulphur content can result in a lowered energy content of the fuel, bringing down fuel efficiency. The increased cost incurred by the petrochemical companies to make their fuels BS6 compliant had to invest highly in the refineries. This increased cost of refining could mean inflation in the fuel prices as also indicated by the government around the period of BS6 norms roll out in April 2020. If the current market analysis reports are something to go by, then there would be a 10-15 % price rise expected in the car rolling out with BS6 engines.


Compatibility is one of the most asked questions after the diktat from the Supreme Court regarding the BS6 change. One of the issues which could arise is, will a BS4 vehicle be able to run on BS6 fuel? So to answer that, for petrol-driven cars, it won't be much of a degradation except for a slightly lowered performance and efficiency as the fuel composition remains almost the same. However, for diesel-driven cars, the reduced amount of sulphur values in the BS6 fuel would mean the lubrication of injectors in diesel engines not getting appropriately lubricated. All of this could lead to injectors getting damaged by the use of BS6 fuel in the BS4 cars. If you are wondering whether BS4 fuel can be used in BS6 cars? Again, the petrol vehicles won't be affected much, but the same can't be said for the diesel vehicles as they would suffer from the DPF(Diesel Particulate Filter) getting clogged up in virtue of the high sulphur content.


There is no question that BS6 emission regulations are the government's best bet to regulate increasing rates of air pollution in major cities across the country. Even if it's for a better tomorrow, there's still an atmosphere of frustration amongst end-users. Hope so we could play a part in easing this tense atmosphere and help you understand a few of the terminologies involved in the BS6 v/s BS4 norms.

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