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BS4 v BS6: Key Differences, Features and Norms

India transitioned from BS4 to BS6 completely on 1st April 2020. BS6 or Bharat Stage 6 is the new emission norm implemented by the Central Government.

  • 24 Jan 2021
  • min read

According to the norms laid down by the Central Government of India, the automotive industry in the country transitioned from BS4 to BS6 from 1st April 2020. BS6 or Bharat Stage 6 (or BS-VI) is the 6th iteration of the emission norm standardised and monitored by the Ministry of Environment and Climate change.

BS4 vs BS6: What is the BS6 norm?

Bharat Stage standards are based on the European (Euro) emission norms, a globally revered standard of vehicular pollution control measures. BS6 or Bharat Stage 6 standard is at par with the Euro 6 emission norms.

BS4 vs BS6: Why did we switch from BS4 to BS6?

Six among the top ten most polluted cities in the world are from India. The severity of air pollution in the country has worsened over time, and greenhouse emission from the motor vehicles largely contribute to the cause. Realising that something has to be done, the Central Government introduced the emission norms back in 2001. Since then, the policies have only been made tighter.

BS4 vs BS6: Key differences between BS4 and BS6

The country shifted from BS4 (BS-IV) to more stringent BS6 (BS-VI) norms. But how do they differ from each other? Let’s take a look.

  • A new BS6 compliant engine now powers new cars and motorcycles
  • BS6 compliant motor vehicles run on more refined BS6 fuel
  • BS6 engines exhaust less volume of harmful gases (nitrous oxide, carbon dioxide, and other greenhouse gases)
  • The combination of hydrocarbon and NOx (nitrous oxide) has declined by 43% in the BS6 diesel engines exhausts
  • The BS6 engines running on BS6 fuel produce 50% less the volume of Particulate Matter (both PM2.5 and PM10)
  • The BS6 compliant diesel cars come equipped with Diesel Particulate Filter (DPF) to filter the exhaust fume
  • The sulphur content in the BS6-grade fuel has significantly been reduced to 10 PPM (Parts Per Million) compared to the 50 PPM in the BS4-grade fuel; an 80% decline in the PPM volume
  • BS6 vehicles come with built-in Onboard Diagnostic (OD) feature

BS4 vs BS6: How does BS6 norm help the environment?

With the air quality worsening in some major Indian cities, it was necessary to take steps to cut down on the pollutants. BS6 or the Euro 6 emission norms address this very need, which is also a global concern. Here are the direct effects of BS6 norms:

Less sulphur content is better for the environment: With more sulphur content, the motor vehicles emit toxic sulphur dioxide gas in the air. This sulphur dioxide reacts with the water vapour in the air and creates H2SO4 or the dangerous sulphuric acid. This reaction causes acid rain. The reduction in sulphur content in the BS6-grade fuel makes it possible to equip vehicles with better catalytic converters that filter the pollutants.

Reduced volume of particulate matter: In the BS6-grade fuel, there is a steep decline (50% decline compared to BS4-grade fuel) in the volume of Particulate Matter (PM2.5 and PM10). PM2.5 is a dangerous pollutant that causes lung cancer.

BS4 vs BS6: Do BS4 vehicles run on BS6 fuel?

Since the BS6 fuel is more refined, the BS4 vehicles can run on it. At least the petrol vehicles don’t face any hiccup. Further, with BS4 diesel cars, companies have claimed that one may not notice any significant issue in the short run. However, experts have expressed their concern stating that using BS6-grade fuel in the BS4-diesel vehicles may show some early wear and tear signs in the long run.

That being said, there are numerous active BS4 diesel vehicles on the Indian roads which are running smoothly on BS6-grade fuel.

BS4 vs BS6: How have the BS6 norms impacted car/motorcycle’s performance?

When the BS6 norms were implemented, the car and motorcycle manufacturers tuned their engines to comply with the norms. This resulted differently in different segments of vehicles. Some of the cars now produce less power than their BS4 variants, albeit the decline is not that significant. On the flipside, BS6 cars offer a better fuel economy. The result is pretty similar in the case of motorcycles and scooters.

Also, the on-paper torque figures for both cars and motorcycles have remained unaltered and, in some cases, have even increased slightly.

It is important to know that with the introduction of BS6 norms, many automobile companies have refrained from launching their diesel vehicles. Whereas, some of the manufacturers have even discontinued their old diesel cars.

Also read:

BS4 vs BS6: Effect of BS6 norms on consumers

The BS6-compliance vehicles got rolled out with a higher price tag, with cars becoming expensive by ₹50,000 to ₹90,000 as compared to their BS4 variants. The price of the newer BS6 compliant motorcycles climbed up by ₹3,000 to ₹10,000.

The fuel price was also speculated to hike because of the huge investment to upgrade the system from BS4 to BS6. However, it was capped by the government and was maintained at par with the existing BS4-grade fuel.

To conclude

It has been more than nine months the BS6 norms have been thoroughly implemented in India. The shift from BS4 to BS6 has skipped the middle stage – BS5, and this was a crucial move on the global scale. Leapfrogging the BS5 norms altogether helped reduce the gap between Indian standards and international standard of the vehicular pollution control measure. Eventually, it is making way for a safer environment and cleaner air to breathe. Also, don't forget to secure your ride with a suitable motor insurance policy. Remember that a car insurance or a bike insurance is mandatory as per the Motor Vehicle Act of 1988.

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