BS4 Vs BS6

Difference between BSIV & BSVI Engine: BS4, BS6 Performance

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.

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, 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 BS6 emission standard is the sixth iteration of the emission norm and comparatively, in terms of reducing pollution compared to the BS4 its very help full. 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 Type	Pollutant Gases	BS6 (BSVI)	BS4 (BSIV)
Petrol Passenger Vehicle	Nitrogen Oxide (NOx) Limit	<60mg>	<80mg>
	Particulate Matter (PM) Limit	<4.5mg/km	-
Diesel Passenger Vehicle	Nitrogen Oxide (NOx) Limit	<80mg>	<250mg>
	Particulate Matter (PM) Limit	<4.5mg/km	<25mg>
	HC + NOx	170mg/km	<300mg>

POLLUTION EMISSION NORMS BS4 VS BS6

I.            BS6 emission standard is the sixth emission norm in the sequence in terms of reducing pollution as compared to retiring the BS4 emission standard. BS4 and BS6 are the assigned emission norms that set the maximum allowable levels of pollutant releases from a motor vehicle engine exhaust.

II.            The BS6 norms vehicles required to emit nearly 60mg/km of NOx (nitrogen oxides) emission, not more than that. Whereas, it was 80mg/km in the case of BS4 norms. Though, the particular matter (PM) limit has also been capped at 4.5mg/km in petrol engines.

III.            In the case of diesel cars emission norms, it’s way strict. NOx emissions should go down from 250mg/km to 80mg/km, HC+NOx emission must go down from 300mg/km to 170mg/km, PM emissions from 25mg/km to 4.5mg/km.

IV.            The level of sulphur and nitrogen oxide content in fuel plays a significant role. BS6 fuel has lower sulphur content than BS4 fuel. The sulphur content in BS6 fuel is five times lower (10ppm) as compared to sulphur content in BS4 fuel (50ppm). And, the nitrogen oxide level for the BS6 diesel engine and petrol engine will be brought down by 70% and 25%.

V.            After BS6 norms come in effect from 1st April 2020, BS6 fuel will start dispensing across all petrol pumps in the country. You can even use BS6 fuel in BS4 or older cars without any trouble.

VI.            Sulphur in fuel helps in proper lubrication inside the engine and burn more efficiently. BS6 contain lower sulphur than BS4 fuel with additives that imitate the lubricating properties of Sulphur.

VII.            Diesel Particulate Filter (DPF) and Selective Catalytic Reduction (SCR) came up with a role in BS6 norm, whereas, it wasn’t available with BS4.

VIII.            With the introduction of BS6 emission norms, Real Driving Emission (RDE) will also be implemented to measure a vehicle’s pollutant emission in real-time conditions. It was not paired with BS4 emission norms.

IX.            Onboard Diagnostic (OD) feature is another change that came up with BS6. It wasn’t introduced with BS4.

X.            A vehicle that has BS6 compliant engine require to fill with BS6 fuel. It won’t adhere to BS6 norms if someone with a BS6 engine uses BS4 engine fuel. Whereas, the emissions will be increased if a vehicle with BS4 fuel engine uses BS6 engine fuel.

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 vapor, 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.

FAQs About BS6 Vehicles:

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.

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