Difference Between BSIV and BSVI Engine

The introduction of the Bharat Stage 6 (BS6) is a major step taken by the Indian Ministry of Road Transport and Highway (MoRTH) to reduce emissions caused by all kinds of transports, including two-wheelers. However, both the emission standards BS4 and BS6 are introduced to lessen vehicle emissions and save the environment. To know the major difference between BS4 and BS6 standards, read the below article.

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Understanding the BSES

The 'BSES' stands for Bharat Stage Emission Standard. BSVI (BS6) is a significant step taken by the Government of India to reduce air pollution as compared to BS4. The government mandated that all vehicles registered and sold after 1 April 2020 must follow the BS6 compliant.

The Government of India has introduced emission norms to reduce harmful gas realized by different types of automobiles, including two-wheelers.

The Indian emission standard BSES is based on European emission regulation that is commonly known as EURO 2, EURO 3, EURO 4, etc. In India, it was introduced in the year 2000 with the moniker BSI (BS1). Further, in 2001, it was BSII (BS2), and in 2005 the BSIII (BS3).

In 2017, the fourth edition of BSIV (BS4) was introduced. With each passing emission norm, the rules became stricter as compared to the predecessors.

Difference Between BS4 and BS6 Automobile Engine

The MoRTH sets pollution standards to regulate the air pollutants emitted out of all the motor vehicles due to the internal combustion of fuel in the engine. BS6 is substantially stricter than BS4. Here is a table showing you a differentiation between these two standards-

Point of Basis BS6 BS4
Sulphur Content Significantly cleaner than BS4 + less Sulphur Higher Sulphur components leading to increased emissions and air pollutants
NOx Emission Not more than 60 mg/km Under BS4, it was 80mg/km
Sulphur Concentration Reduced to five times. Currently, it is 10ppm It was 50ppm which was substantially higher
Lubricating Characteristics Contains mimic Sulphur’s lubricating characteristics for better performance Only uses real Sulphur which emit more pollutants
Onboard Diagnostic (OD) Available in BS6 Not available in BS4
Real Driving Emission Driving Emission Standards are strictly enforced in BS6 to track pollutant emissions in real-time situations The real-time situation cannot be traced in BS4 engines

Moreover, here is a table below that highlights the changes in the emission levels of BS6 versus BS4-

Type of Fuel Engine Pollutant Gases BS4 Emission Level BS6 Emission Level
Petrol Engine Vehicle Particulate Matter (PM) Limit NIL <4.5mg/km
Nitrogen Oxide (NOx) Limit <80mg> <60mg>
Diesel Passenger Vehicle Particulate Matter (PM) Limit <25mg> <4.5mg/km
Nitrogen Oxide (NOx) Limit <250mg> <80m>
Hydrocarbons + Nitrogen Oxide (HC + NOx) <300mg> 170mg/km

How Does a BS6 Engine Works?

In the BS6 engine, the converter assists the Selective Catalytic Reduction (SCR) mechanism present in the Nitrogen Oxide to transform into Diatomic Nitrogen or H2O. In this. SCR system uses fuel fumes fluid to minimize the NOx levels.

If the exhaust fumes come in contact with AdBlue liquid, the urea is transformed into CO2 or ammonia. Also, the NOx is transformed into nitrogen & water vapors and hence, helps in minimizing the emission.

Effect of BS6 Emission Norms on the Two-wheeler Performance

With the advancement in engine technology, BS6 has made quite improvements in every term. Under this norm, two-wheeler manufacturers have to install gasoline injection systems to reduce toxic exhaust emissions.

As the BS6 two-wheeler engines are less powerful and more fuel-efficient, they have reduced carbon emissions in the environment. Ultimately, this emission norm has improved the overall performance of a two-wheeler.


Moving to more rigorous pollution emission norms, the Indian government has implemented BS6 to reduce pollution levels and save our environment. If you are planning to buy a new two-wheeler, ensure that you will not substitute BS6 standards with its predecessors just to save pennies. Moreover, get the right two-wheeler insurance policy to cover your possession from several unforeseen instances.

Written By: PolicyBazaar - Updated: 07 October 2022
Disclaimer: Policybazaar does not endorse, rate or recommend any particular insurer or insurance product offered by an insurer.

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