To regulate the pollution emitted by cars and two-wheelers, the government of India has put forth regulations known as Bharat Stage Emission Standards (BSES). The Central government has mandated that all vehicle manufacturers, both two-wheelers and four-wheelers, should manufacture, sell and register only BS6 (BSVI) vehicles from 1 April 2020.
In this article, you will learn about BS4 vs BS6 engine, major differences and performance of the new BS6 engine.

Difference between BSIV & BSVI Engine: BS4, BS6 Performance - Acko

What is BS4 (BSIV)?

Before we understand about BS6 emission or BS6 compliant engine, let’s understand the current BS4 (BSIV) emission norms, engine, performance, and its significance. 

The BSES, which is the governing organization for emissions from all types of vehicles in the country, introduced the first emission norms with the name ‘India 2000’ in the year 2000. BS2 and BS3 were introduced in 2005 and 2010, while BS4 norms came into effect in 2017 with stricter emission standards or norms.

Among the regulations set by the governing body, emission-related changes included tailpipe emissions, Electronic Control Unit (ECU), ignition control, etc. The most visible change was the AHO (Automatic Headlamp On), this is one of the norms under the BS4 which catered to the safety aspect of the new emission standards.

What is BS6 (BSVI)?

The governing body, Bharat Stage Emission Standards (BSES), regulates the output of pollutants from vehicles plying in the country. The Central Pollution Control Board which falls under the Ministry of Environment, Forest and Climate Change sets the standards to regulate emissions from vehicles in India.

The first emission standard or norm, introduced in the year 2000, was known as ‘India 2000’ and later, BS2 and BS3 were introduced in 2005 and 2010, respectively. While the first three emission norms were introduced at regular intervals, BS4 was introduced in 2017, after a gap of seven years.

The BS6 emission standard is the sixth iteration of the emission norm and comparatively, it’s a substantial leap in terms of reducing pollution compared to the outgoing BS4. This is also because the BS5 (BSV) has been skipped in an effort to move to better emission norms.

Difference Between BS4 (BSIV) and BS6 (BSVI):

Both BSIV and BSVI are emission norms that set the maximum permissible levels for pollutants emitting from a car or a two-wheeler exhaust. Compared to the BS4, BS6 emission standards are stricter. While manufacturers use this change to update their vehicles with new features and safety standards, the biggest or the significant change comes in the form of stricter permissible emission norms.

The below table offers an insight into the change in the permissible emission levels of BS6 vehicles compared to BS4 vehicles:

Fuel TypePollutant GasesBS6 (BSVI)BS4 (BSIV)
Petrol Passenger VehicleNitrogen Oxide (NOx) Limit<60mg><80mg>
Particulate Matter (PM) Limit<4.5mg/km-
Diesel Passenger VehicleNitrogen Oxide (NOx) Limit<80mg><250mg>
Particulate Matter (PM) Limit<4.5mg/km<25mg>
HC + NOx170mg/km<300mg>

What are BSI, BSII, BSIII, BSIV and BSVI Emission Norms?

These are emission standards set by the governing body Bharat Safety Emission Standard (BSEB) to regulate the output of pollutants from vehicles plying on the road. The Central Pollution Control Board, under the Ministry of Environment and Forest and Climate Change, sets the permissible pollution levels and timeline to implement the same by vehicle manufacturers. 

The abbreviation of ‘BS’ is Bharat Stage and is suffixed with the iteration of the particular emission norms. The Indian emissions standards are based on the lines of European norms commonly known as EURO 2, EURO 3, and so on. The first regulations with the moniker India 2000 were introduced in 2000, with the second and third iteration introduced in 2001 and 2005 with the moniker BSII (BS2) and BSIII (BS3), respectively.

The fourth iteration BSIV or BS4 was introduced in 2017 and the delay between the introduction of BS3 and BS4 resulted in fast-tracking the BSVI or BS6 emission instead of BSV or BS5 norms. Each of these emission norms has stricter emission standards compared to its predecessors.

The table below offers an insight into the implementation timelines of the emission norms:

Emission StandardReferenceYear of Introduction
India 2000EURO 12000
Bharat Stage II (BS2)EURO 22005
Bharat Stage III (BS3)EURO 32010
Bharat Stage IV (BS4)EURO 42017
Bharat Stage V (BS5)EURO 5To be skipped
Bharat Stage VI (BS6)EURO 62020

Impact of BS6 on CNG Cars:

Vehicle manufacturers will have to make minor changes or modifications to their diesel and petrol engines for the usage of CNG on BS6 vehicles. It’s only a matter of time before manufacturers start offering CNG compliant BS6 engines in the country. CNG powered BS6 cars or vehicles could be a stop-gap arrangement before the era of electric and hybrid vehicles are sold in the country.

How Do BS6 (BSVI) Diesel Engines Work?

The Selective Catalytic Reduction (SCR) unit converts nitrogen oxide (NOx) into diatomic nitrogen and water (both are harmless products) with the help of a catalyst. The SCR unit uses AdBlue or diesel exhaust fluid to reduce NOx emissions. This fluid is made up of two parts – urea and deionized water. When exhaust gases come in contact with the AdBlue fluid, urea is converted to ammonia and carbon dioxide and in turn, the ammonia converts NOx into nitrogen and water vapour, thereby reducing pollutants.

The AdBlue will be filled in a 10-litre capacity tank in smaller passenger vehicles. Currently, AdBlue is being sold by distributors at a premium rate; however, with the rapid increase in sales of BS6 diesel engines, the cost of AdBlue is expected to decline.

List of BS6 Cars Available in India 2019:

Ahead of the deadline of the implementation of BS6 compliant vehicles from 1 April 2020, several car and bike manufacturers have launched BS6 cars and bikes in India. Below is the list of BS6 cars and two-wheeler currently available to buy:

BS6 Sedan Cars:

  • Maruti Suzuki Dzire
  • Hyundai Elantra
  • Mercedes Benz E-Class
  • Audi A6

BS6 Hatchback Cars:

  • Maruti Suzuki Alto 800
  • Maruti Suzuki S-Presso
  • Hyundai Grand i10 Nios
  • Maruti Suzuki Swift
  • Maruti Suzuki Wagon R 1.2-litre
  • Maruti Suzuki Baleno
  • Toyota Glanza

BS6 MPV Cars:

  • Maruti Suzuki Ertiga
  • Maruti Suzuki XL6


  • Kia Seltos
  • Jeep Compass

BS6 Crossover Cars:

  • Maruti Suzuki XL6
  • Maruti Suzuki S-Presso

List of BS6 Bikes/Two-Wheelers in India 2019:

Here is the list of BSVI bikes in India that has been launched much before the deadline of 1 April 2020:

  • BS6 Scooters:
    • Honda Activa 125
  • BS6 Two-Wheelers:
    • Hero Splendor iSmart 110
    • Honda SP 125
    • Yamaha FZ V 3.0
    • Yamaha FZ S V 3.0
    • Jawa Perak

Why are there no Light switch on BS4 Bikes?

All two-wheelers, including motorcycles and scooters that were manufactured from 1 April 2017 featured the Automatic Headlamp On (AHO). As the moniker suggests, all two-wheelers are required to have the headlights on at all times. In compliance with the BS4 norms, all new two-wheelers will not have a light switch for the headlight, since it needs to be always on. However, the pass and the low and high beam light switch were kept untouched.

The reason behind the introduction of AHO was keeping both the rider’s and pedestrian’s safety. The light remains on during the day as well, which makes it visible to passersby. 

FAQs About BS6 Vehicles:

Here are the frequently asked questions about BS6 cars and bikes in India:

What happens if you fill BS6 fuel in BS4 car?

You can fill BSVI fuel in BSIV cars or older models. Sulphur in fuel acts as a lubricant inside the engine and burns efficiently. The BSVI fuel has lesser sulphur; however, it contains additives which helps in the lubrication of the engine.

Can BS6 engine run on BS4 fuel? Does it meet the BS6 emission standards?

The emission from the tailpipe of a BS6 vehicle should match the BS6 norms and this is possible only if BS6 fuel is filled in BS6 cars. While a BS6 car can run on BS4 fuel, it may not comply with the BS6 norms.

Is BS6 fuel expensive compared to a BS4 fuel?

Prior to the nationwide rollout of BS6 fuel, it has been implemented in Delhi and the NCR and the prices are not different between BS6 and BS4 fuel. However, this may change once it’s implemented across the country due to input costs incurred by the Oil Marketing Companies (OMCs) towards upgrading their facilities.

Can I convert my old car to meet BS6 emission norms on my own?

You can convert your old car to BS6 standards; however, it requires time and money. Also, it’s illegal.

What’s next after BS6?

Currently, there are no new emission norms has been set by the governing body. However, there may be a second version of the BS6 which will include Real Driving Emissions (RDE) cycle. As per this law, the Automotive Research Association of India (ARAI) will test new vehicles in real-world conditions to ascertain the level of pollution. Currently, the test is done in a controlled environment.

What are CAFE norms?

The Central government has proposed to introduce Corporate Average Fuel Efficiency (CAFE) in sync with the global auto industry. Under these norms, cars are expected to be 30% fuel efficient from 2022 and by the end of 2021, it’s expected to be increased by another 10%. Through CAFE norms, fuel efficiency will be decided on how many litres does a vehicle consume while running 100kms.

Why the skip from BS4 to BS6 and not BS5?

The first emission norm was introduced in 2000, while the second and third iteration was introduced in 2005 and 2010. The BS4 was implemented in 2017, the big gap prompted the government to skip BS5 and jump to BS6 in an effort to reduce pollution in the country.

Do BS4 vehicles require a pollution certificate?

Yes, all vehicles plying on Indian roads require Pollution Under Control (PUC) certificate as per the Motor Vehicle Act.

What will happen to BS4 vehicles after 2020?

No new BS4 vehicles will be manufactured or registered by the RTO after 1st April 2020 when the BS6 emission norms are implemented. However, existing BS4 vehicles will be allowed to run on public roads. Currently, there is no deadline set for BS4 vehicles to stop playing on public roads.

What is the difference between a Euro 6 and a BS6 engine?

The emission limits for both the Euro 6 and BS6 engine are numerically equivalent, although it could be slightly tweaked to Indian standards.

What is the difference between BS4 and BS6 car performance?

The BSVI engine is relatively cleaner than the BSIV engine leading to lower combustion. Add new components to the exhaust system and it reduces the overall performance of the car to a certain extent, although not that significant. That said, vehicle manufacturers are developing engines which offer a balance between performance, efficiency and emissions.

What is the difference between BS4 and BS6 cars fuel economy?

The difference between BSIV and BSVI cars’ fuel efficiency is minimal. The BS6 Maruti Dzire has an ARAI certified fuel efficiency of 21.21 km/l while the outgoing BS4 Maruti Dzire returned a mileage of 22 km/l. A slight decline in mileage although not significant.

News Related to BS6 and BS4 Engine:

BS6 Norms for Quadricycles Announced

– May 27, 2020

The Government of India has announced the BS6 norms for quadricycles in the country. Quadricycles are categorised as L7 in India. While the BS6 norms were rolled to other categories of vehicles, the L7 category was left out. The announcement by the Ministry of Road Transport and Highways has given approval for the full-scale manufacturing of quadricycles in the country. With the latest notification, the process of BS6 for all categories of vehicles is completed. The government said the issued norms were at par with the European Union’s WMTC cycle. Quadricycles are 4-wheeled vehicles that are quite small in size with a length of 3,000mm, a width of 1,500mm and a height of 2,500mm and the maximum top speed is restricted to 70kmph.

Vehicle Scrappage Policy to Improve Auto Manufacturing Industries in India: Govt.

– May 26, 2020

The Union Transport Minister said that the government is all set to start the vehicle scrappage policy. Recycling clusters will be built near ports. He also said that through this initiative India, in five years, will emerge as the world’s leading automobile manufacturing hub. Under the policy, old cars, buses and trucks will be scrapped. He also added that the depth of the country’s ports will be increased by 18 meters to accommodate recycling clusters. The recycled material will be utilised by automobile manufacturers to reduce the cost of manufacturing new vehicles.

BS4 Vehicles Banned From Being Sold From 1 April 2020

– April 1, 2020

The road transport ministry has directed all states and Union Territories (UT) in the country to stop selling BS IV vehicles in India from 1 April 2020. With the ongoing lockdown, there are several unsold BS4 vehicles; however, the centre has directed all states and UT to comply with the directive of selling only BS6 vehicles from 1 April 2020. The Ministry in its directive has also attached the Supreme court order to sell 10% BS4 vehicles of the total unsold stock, but this does not apply to Delhi and NCR region.

Indian Oil Corporation Begins Dispensing Cleaner BS6 Petrol and Diesel in India

– March 24, 2020

India’s largest oil manufacturing company (OMC)., Indian Oil Corporation (IOC) became the first company to start selling the cleaner BS6 petrol and diesel in the country. From 1 April 2020, all petrol pumps will begin selling the BS6 petrol and diesel in adherence to the BS6 norms which kicks in from 1 April 2020. The company’s chairman said that more than 28,000 IOC petrol bunks have begun selling BS6 fuel in the country ahead of the deadline. BS6 fuels are being introduced in tandem with the deadline to begin selling only BS6 vehicles in the country from the same date. BS6 fuels are much cleaner compared to the BS4 fuel since it contains less sulphur, leading to lower emissions or pollution.

India to Switch to BS6 Petrol and Diesel From 1 April 2020

– March 4, 2020

India’s largest oil company Indian Oil Corporation (IOC) announced that it is ready to supply BS6 petrol and diesel from 1 April 2020. The new BS6 fuels will cost marginally higher than the BS4 fuels that are being sold currently. IOC said that the BS6 fuels will have a sulphur content of 10 parts per million (ppm) compared to 50ppm in the BS4 fuels. IOC has spent close to Rs.17,000 crore towards upgrading its refineries to BS6. The Oil Marketing Company (OMC) said that it has switched to BS6 fuel production a fortnight ago and its containers and depots are ready.