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What is a BS4 engine and how does it compare to a BS6 engine?

By Finserv MARKETS - Nov 28,2019
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BS4 Details

A three-judge bench of the Supreme Court, headed by Justice Madan B Lokur, in October announced that no Bharat Stage 4 (BS4) vehicle shall be sold across the country, effective from April 1, 2020. Since the time of this announcement, many have been speculating about the future of the automobile industry. Amid this discussion, many remain confused about the evolving technology. If you are among them or want to know more about the BS4 and BS5 engine standards, then, by all means, read on.

What is Bharat Stage?

Introduced in 2000, the Bharat norms are emission control standards issued by the government. Based on European standards, there are limits for the release of air pollutants – nitrogen oxides, carbon monoxides, hydrocarbons, particulate matter, sulphur oxides- from equipment using internal combustion engines, including vehicles. The higher the stage, the stricter the norms.

Bharat Stage4 and 5

The (BS6) norm is the sixth order for vehicular emissions, BS4 being the fourth. Due to a rampant increase of air pollution in Indian cities, it was decided that we directly jump to BS6 standards, skipping BS5. BS6 is a more restrictive norm, and with its application, the Indian vehicular standards will be at par with the developed European and American nations. More importantly, this will give India’s long battle with air pollution a significant push.

Difference between Bharat Stage4 and Bharat Stage5

BS4 Details

Source: autbotindia

  1. Will require a fuel change: The BS6 compliant engine will require BS6 fuel for it to be effective. A BS6 vehicle using BS4 fuel, although will function, it will not adhere to the BS6 pollution norms. In India, the oil companies have already started distributing BS6-grade Petrol and Diesel in their respective gas-stations.
  1. Pollutants: The BS4 engine releases 50 parts per million (ppm) sulphur whereas a BS6 engine emits around 10ppm. Besides under BS6, particulate matter emission for diesel cars and nitrogen oxide levels are expected to be substantially lower than in BS4.
  1. Performance: A cleaner engine attributes to a slower combustion process. Hence, lowering these environmental emissions more often than not, take a hit on your car’s performance. The exhaust modifications necessary for BS6 compliance further reduce the overall performance of the vehicles. Therefore, there is no doubt that BS6 compliant cars will dwindle your car’s performance. However, car manufacturers like Mahindra and Tata have invested a lot of money into their research and development wing. It is being done to balance the car’s performance.
  1. Fuel Economy and Mileage: Due to dwindled performance, the mileage of BS6 equipped cars takes a hit. The recently launched Maruti Suzuki Dzire gives a mileage of 21.21 km/l in comparison to 22km/l that was returned by the BS4 compliant Dzire.
  1. Introduction of DPF (Diesel Particulate Filter) and SCR (Selective Catalytic Reduction) for Diesel engines with BS6 vehicles: DPF is a device designed to eliminate diesel particulate matter, also known as soot, from the exhaust gas of a diesel engine. Another most significant difference being the mandatory OBD (Onboard Diagnostics) for all vehicles. Such OBD will monitor emission levels and give out warnings.


The Indian automotive industry has invested billions for the eventual phase-out of BS4 and subsequent introduction of BS6 compliant vehicles. One of the most critical challenges with the BS6 upgrade is that the cost of manufacturing will rise.

A few car analysts even claim that car prices can soar by 10%-15%. Such a hike in car-price can be neutralised to an extent by intelligently buying other car essentials, such as car insurance. You can opt for comprehensive car insurance available on Finserv MARKETS, in a smooth, hassle-free manner and with minimal documentation. Another challenge associated is the fuel and BS4 diesel engine relation. Even though for petrol car owners supporting a BS4 engine, the introduction of BS5 fuel is not a case of worry – as the BS4 petrol and BS6 petrol have minimal differences in terms of their chemical composition, while for diesel car owners this is not the case.

BS4 diesel has a much higher Sulphur (50 ppm), whereas BS6 diesel contains only 10 ppm of Sulphur traces, which inhibits air pollution. Sulphur is an essential constituent for diesel engines as it acts as a lubricant for diesel injector (diesel engine relies on the injector to ionise the fuel for it to become combustible). Prolonged usage of BS6 diesel in a BS4 compatible car, causes this injector to wear out prematurely owing to less lubrication.

Subsequently, the diesel car owners will have to upgrade their vehicles by either modifying their injector lubricant or by purchasing a new car. If the latter is the case, make sure that apart from meeting fuel emission standards, you also upgrade your car-insurance for a smooth tension free ride. This can be done by applying for Bajaj car insurance on Finserv MARKETS, where you can enjoy cashless servicing at more than 4,000 garages across the country.

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