If you’ve bought a car in the last few years, you’ve probably heard terms like BS4 and BS6. But what do these “BS” norms actually mean, and how do they affect how long your car can stay on the road? Let’s break it down in simple words.
What Are BS Norms?
“BS” stands for Bharat Stage, the emission standards set by the Indian government to control air pollution from vehicles.
These norms decide how much your car can pollute — basically, how clean the engine runs.
BS4 was the previous emission standard implemented nationwide in 2017.
BS6 is the current standard that came into effect from April 2020.
BS6 is much stricter and cleaner compared to BS4 — the emissions are almost 70–80% lower.
Difference Between BS4 and BS6 Vehicles
Let’s understand the major differences between the two:
Emission Levels:
BS6 vehicles release much fewer pollutants like nitrogen oxide (NOx) and particulate matter.Fuel Type:
BS6 vehicles need low-sulphur fuel, which is cleaner and helps in better engine performance.Technology:
BS6 engines use advanced tech like DPF (Diesel Particulate Filter) and SCR (Selective Catalytic Reduction) to control pollution.Maintenance & Cost:
BS6 vehicles can be slightly more expensive due to new technology, but they are better for long-term performance and environment.
How BS Norms Affect Car Lifespan
Pollution norms directly decide how long a car can stay on the road — especially in cities like Delhi NCR, where the government follows strict NGT (National Green Tribunal) rules.
Here’s how it works:
Petrol Cars: Allowed for 15 years from registration.
Diesel Cars: Allowed for 10 years from registration.
So, whether your car is BS4 or BS6, the rule applies the same — but the cleaner your engine, the better it is for future regulations.
Will BS4 Cars Be Banned?
In some regions like Delhi NCR, older BS3 and BS4 commercial vehicles are already facing restrictions due to high pollution levels.
BS6 vehicles, being cleaner, are likely to have a longer regulatory lifespan and face fewer restrictions in the coming years.
Should You Upgrade from BS4 to BS6?
If your BS4 vehicle is running fine and meets PUC norms, you don’t need to worry immediately.
But if you’re planning to buy a new car, BS6 is the future-proof choice — it offers:
Better mileage
Lower emissions
Smoother performance
Compatibility with upcoming policies
Final Thoughts
BS norms are not just about pollution — they’re about the future of clean mobility in India.
BS6 cars are not only better for the environment but also a smarter investment in the long run.
Want to check how long your car can legally stay on the road as per current pollution norms?
Use our free tool — CarExpiryCalculator.com — and find out your car’s expiry year in seconds!