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BS4 vs BS6

The Government of India announced that all the vehicles plying on Indian roads must be BS6 compliant effective from 1 April 2021. Earlier, most of the vehicles in India were BS4 compliant. However, with change in emission standards, the automobile companies will have to manufacture vehicles which meet the latest emission guidelines.

What is BS4?

Bharat Stage Emission Standards (BSES) is the government organisation which sets the emission guidelines for the vehicles plying on the roads of India. BS2 and BS3 had come in the years 2005 and 2010 respectively following which the BS4 was introduced in 2017.

BS4 standards had stricter emission rules and guidelines. There were certain emission-related changes set in motion such as ignition control, Electronic Control Unit (ECU), tailpipe emission, etc. One of the biggest changes related to the BS4 emission standards was the Automatic Headlamp On (AHO).

What is BS6?

BSES instead of introducing BS5, straightaway introduced the BS6 emission standards so as to move to better and stricter emission norms. The BS6 emission norms aims at reducing pollution much more significantly as compared to the standards set by BS4.

Difference between BS4 and BS6

The table below provides the difference between BS4 and BS6 emission standards:

Type of fuel Pollutant gases BS6 BS4
Diesel passenger vehicle Particulate Matter (PM) Limit <4.5mg/km <25mg>
HC + NOx 170mg/km <300mg>
Nitrogen Oxide (NOx) Limit <80mg> <250mg>
Petrol passenger vehicle Particulate Matter (PM) Limit <4.5mg/km
Nitrogen Oxide (NOx) Limit <60mg> <80mg>

Pollution Emission Norms

  • BS6 emission standard is the sixth emission guidelines introduced by BSES after BS4 emission standards were made redundant. The new emission guidelines mention the level of pollutant gas the exhaust engine of a vehicle is allowed to release.
  • The new BS6 emission norms allow petrol passenger vehicles to emit only up to 60 mg of pollutant gases as compared to 80 mg allowed by the BS4 emission norms. The Particulate Matter (PM) Limit is set at 4.5 mg per km.
  • The PM Limit for diesel passenger vehicles have been set at 4.5 mg per km. The Nitrogen Oxide limit has been brought down to 80 mg from the earlier acceptable limit of 250 mg. The HC + NOx limit has been set at 170 mg per km.
  • The level of Sulphur and nitrogen oxide has also been brought down significantly. BS6 fuels contain lower level of Sulphur while the nitrogen dioxide level for BS6 diesel and petrol-based vehicles have been reduced by 70% and 25% respectively.
  • BS6 fuels will be sold across all the petrol pumps in India once the norms come into effect from 1 April 2021. You can use BS6 fuel in BS4 vehicles without any problem.
  • Sulphur in fuels have lubricating properties which provides lubrication inside the engine and burn in a more efficient manner. The BS6 fuel despite containing low level of Sulphur will have additives which will provide lubrication inside the engine.
  • The BS6 norms will not have place for Diesel Particulate Filter (DPF) and Selective Catalytic Reduction (SCR).
  • The BS6 norms will also introduce Real Driving Emission (RDE) which will help in computing the level of pollutant emission by a vehicle in real-time condition.
  • The BS6 norms will introduce another feature called Onboard Diagnostic (OD).
  • If you own a BS6 compliant vehicle, then you can only fill BS6 fuel. As per the norms, you cannot use BS4 fuel in your BS6 compliant vehicle. The emissions will rise if a BS4 compliant vehicle will use BS6 fuel.

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