BS6 Regulations: How Does it Affect You

The Indian government has been steadily moving towards reducing pollution in India. The government based the Indian emissions regulations on the European standards. The Bharat Stage Emission Standards were introduced in 2000 and has gone through four iterations, with the latest standard being Bharat Stage 4 (BS4), introduced in 2010.

From April 2020, the country is going to make a significant shift to Bharat Stage 6 (BS6) emission norms, skipping Bharat Stage 5. With this move, India will mirror European regulations rather than lag behind by five years.

What are the BS6 Regulations?

BS6 regulations have a direct effect on the fuels and the internal combustion engine. These regulations will bring significant changes to the cars and fuel sold in India.

Fuel Content

With regard to fuel, the BS6 regulations greatly reduce the sulphur content currently present in BS4 fuels. Sulphur is a natural part of all fuels and needs to be removed by refiners to reduce the sulphur in fuels. It is the burning of this sulphur component that produces the toxic particulate matter.

Sulphur in petrol fuels is processed to contain only 10 parts per million (ppm), which is within the regulations for BS4 and BS6 petrol fuels. The major difference is visible in diesel fuels. Currently, BS4 diesel contains 50 ppm of sulphur

Emissions comparison between BS4 and BS6 engines

BS6 and BS4 petrol fuels are almost identical in their contents. The shift in regulations targets the high sulphur content in BS4 diesel fuels. BS4 diesel contains as much as 50 parts per million (ppm) of sulphur, which will be brought down to parity with petrol at 10 ppm of sulphur. The effect? A reduction of 80% in particulate matter emissions and a 60% decrease in Nitrous oxide (NOx) emissions.

Effect of the Regulations

To comply with the regulations, manufacturers will need to redevelop their engines to burn the fuel cleanly. This will be achieved by reworking the injection systems as well as the combustion process. Manufacturers will also have to treat the exhaust fumes of their vehicles to remove particulate matter and NOx. This is done by installing a Diesel Particulate Filter (DPF) and Selective Catalytic Reduction (SCR) system. The DPF filters the particulate matter and soot produced by the engine while the SCR injects AdBlue, a water-based urea solution, to convert NOx emissions into Nitrogen and Oxygen gases.

Cutout of Diesel Particle Filter (DPF)
Cutout of DPF system showing the filters that scrub exhaust of particulate matter

The strict regulations are designed to ensure that vehicle emissions are significantly reduced. The introduction of BS6 regulations will have a knock-on effect on the automotive market. Due to the significant costs involved in developing new engines for the new fuels, prices of new cars will increase by ₹10,000-20,000 for petrol variants and ₹80,000-₹1,00,000 for diesel variants.

What does it mean for BS4 cars?

From April 2020, new BS4 cars will no longer be sold by manufacturers and new BS4 cars will not be registered after April. However, cars bought till March 2020, will be registered till the end of the car’s validity mentioned in the RC.

This means that while you may not be able to buy a new BS4 car post-April, you will still find used BS4 cars on the used car market, at least till 2035. Those thinking about buying a used car in this period of transition should not be hesitant. So if you are a current owner or you’ve recently bought a new BS4 car, there is no rush to sell off your BS4 car and upgrade to a BS6 car in the immediate future.

Also Read: Should you Upgrade to BS6 in 2020?

Current owners of older BS4 vehicles thinking of upgrading to BS6 may get good deals when they sell their used cars. As popular models go off the new car market, the demand is expected to increase for these models. You my find it easier to sell your car during this period and for prices that will provide you great value.

BS4 or BS6 Fuel

As mentioned earlier, BS4 and BS6 fuels are significantly different from each other. There are questions around whether BS6 fuel can be used in BS4 engines or whether BS4 fuel can be used in BS6 engines. In both cases, the answer is different.

Also Read: 8 Popular BS4 Cars to be Discontinued

There is little difference between BS4 and BS6 petrol fuels. Thus, filling BS4 fuels in your BS6 car or vice versa, will have no significant effect on the engine.

Petrol and Diesel fuel pump nozzles
Keep track of the fuel you fill your car with

With diesel engines, it becomes slightly more complicated. BS4 diesel fuel still contains sulphur which will produce soot and particulate matter. These pollutants will clog up the DPF, which will reduce the filter’s effectiveness. If the car isn’t properly maintained to clean the pollutants, it could lead to the filter needing a costly replacement.

BS6 diesel fuel is also not the best fuel for BS4 engines. The injectors in BS4 diesel engines are designed with the sulphur providing lubrication. With the lower sulphur content in BS6 diesel, the injectors will be subjected to slightly increased wear. Regular maintenance should see your BS4 diesel car continue smoothly till the end of its life.


The Indian government is introducing sweeping changes in an effort to tackle the growing pollution crisis in India. By moving directly to BS6, the government has shown a clear intent to reduce emissions at a time when car sales are expected to grow, despite the industry slowdown. There will be a transition period as both BS4 and BS6 ply Indian roads for a few years. However, the introduction of BS6 fuel should ensure that even BS4 engines have cleaner emissions.

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