BS4 vs BS6 Engines and Beyond: How BS7 Will Change the Game

Arjun remembers his 21st birthday until today. It was when his dad gifted him his new BS4 car. His happiness knew no bounds! The engine roared as he put the keys, and he was excited to show his friends his new vehicle. Years later, he thought the city felt dusty and the driving wasn't smooth. After that, Arjun moved to a BS6 vehicle.

The air felt a bit cleaner, the ride was smooth, and the engine ran quietly. That change showed the significant impact that new engine rules can have. BS7 is on the horizon. Arjun became even more excited by this. He was curious to know how BS7 cars will work. If the transition from BS4 to BS6 was impressive, then BS7 might be much more so!

Are you excited like Arjun as well? Then, let's examine the development from BS4 to BS6 in more detail and see what comes next.
 

Understanding BS4 Engines

Once upon a time, buying a car didn’t mean worrying about emissions or air quality. For many, that was the BS4 era. Introduced nationwide in 2017, BS4 (Bharat Stage 4) represented a serious attempt to make vehicles cleaner and more responsible. It replaced BS3 and stayed the standard until BS6 came along in 2020.

To put it simply, if an engine is the heart of a car, fuel is its lifeblood. BS4 engines were designed to burn cleaner. The big targets were Nitrogen Oxides (NOx) and Particulate Matter (PM), the tiny soot particles you don’t see but breathe in anyway. It wasn’t perfect, but it got both manufacturers and drivers to start paying attention.

It might seem obvious now, but back then, this was a great shift. The BS4 era nudged everyone (drivers, engineers, and policy makers) toward thinking about responsibility in a very tangible way.
 

Key Features of BS4 Technology

So what changed with BS4? Well, several things, and most of them were quietly brilliant. These weren’t flashy upgrades you’d notice immediately, but they made the car smarter, cleaner, and safer.

• Catalytic Converters
  BS4 cars had catalytic converters. They’re small, tucked in the exhaust, doing work most people never think about. Exhaust gases flow through, chemical reactions happen, and harmful stuff like carbon monoxide, hydrocarbons, and NOx get converted into safer gases like carbon dioxide, nitrogen, water vapour. You can’t see it, can’t hear it, but it makes a difference.
• On-Board Diagnostics (OBD-II)
  OBD-II was like giving the car a voice. Suddenly, it could check its own health. If something went wrong, a sensor failing or emissions popping up, it would light up a warning on your dashboard. It was the first time cars could “talk back,” so to speak, and tell you they weren’t feeling well.
• Evaporative Emission Control (EVAP)
  Before BS4, petrol could evaporate from your tank and vanish into the air, releasing unburned hydrocarbons. EVAP systems changed that. They capture these vapours, store them, and feed them back into the engine to burn properly. It’s invisible, but it stops your car from polluting while just sitting there.
• Anti-lock Braking System (ABS)
  ABS became mandatory for passenger cars, keeping you safer during sudden braking. It was a reminder that clean cars also needed to be safe cars.

Put it all together, and BS4 vehicles were smarter, safer, and far cleaner than their predecessors. They weren’t perfect, but they started a conversation about responsibility in driving. BS4 set the stage for BS6. Without it, the leap to modern standards might never have been possible.

It’s easy to forget now, but BS4 was our first real taste of what responsible mobility could look like: cleaner air, smarter machines, and technology quietly working to make your drive better. BS4 was the step that led the journey toward cleaner engines and smarter cars was far from over.
 

The Leap to BS6

If BS4 was a significant step, then BS6 was a giant leap. A quantum jump, really. The transition in 2020 was a complete overhaul of our automotive standards. It catapulted India into a league previously occupied by advanced markets like Europe.

We're talking about slashing some of the most harmful pollutants by a massive margin. It was around a 68 % cut in Nitrogen Oxides (NOx) for diesel engines and roughly an 80 % drop in particulate emissions for diesels. Petrol engines also saw tighter limits, including new particulate-matter controls for direct-injection models. Yes, you read that right. This was a firm push towards a future with clearer skies.

But such a radical reduction didn't come from simple tweaks. It required a technological revolution under the hood. Car manufacturers had to go back to the drawing board. They introduced more advanced and precise fuel injection systems, upgraded the Engine Control Units (ECUs) and introduced some hardware that was uncommon to the Indian market.

The most talked-about of these?

Among the most significant additions were Diesel Particulate Filters (DPF), which trap and burn soot, and Selective Catalytic Reduction (SCR) systems that use a urea-based fluid called AdBlue to neutralize NOx. Petrol engines, especially those with direct fuel injection, began to use Gasoline Particulate Filters (GPF) to control fine exhaust particles.

This leap was so substantial that BS4 vehicles could no longer be sold as new after March 31, 2020, effectively ending their production. It changed everything from the fuel we use (remember the shift to BS6-grade fuel with sulfur content reduced from about 50 ppm to just 10 ppm?) to the very engineering of our vehicles. And that leads us to the most obvious question: what does this all mean when you compare them side-by-side?
 

Comparing BS4 and BS6 Engines

Here’s a clear explanation to show you exactly where your money and our environment are getting the upgrade:

A BS4 car was responsible for its time, but a BS6 vehicle reflects today’s environmental priorities and global standards.
 

BS7 on the Horizon

Just when we were getting comfortable with BS6, the conversation is already shifting. You might have heard whispers about Bharat Stage 7, or BS7. And it’s true, the wheels of progress are already in motion for the next big leap.

But here's the most important thing to know right now: Some industry estimates suggest 2026–27 as a possible timeframe for initial phases, though full rollout might take longer. No official date has been fixed.

The reason for this long lead time is simple: BS7 is expected to push norms closer to zero for conventional engines, combining stricter tailpipe limits with control over non-exhaust emissions. While BS6 focused on making the internal combustion engine as clean as humanly possible, BS7 is expected to look beyond it. The core idea is moving from "reducing tailpipe emissions" to aiming for virtually zero emissions from new vehicles.

How? The talk of the town is that BS7 norms might be the first to seriously push for a massive adoption of hybrid and electric vehicles. The stricter norms may favor hybrids and EVs, making compliance much tougher for conventional petrol and diesel engines in many segments.

Think of it as the final evolution of the emission norm story, one that seamlessly blends into the electric vehicle (EV) revolution. It’s fundamentally changing what comes out of the tailpipe.
 

What BS7 Means for Consumers and the Industry

So, what does this futuristic BS7 world mean for you, the car owner, and for the entire automotive ecosystem? Let's break it down.

➔ For the Industry: A Total Transformation

For car manufacturers, BS7 will be the biggest challenge yet. It’s not just about adding a new filter or sensor. It will likely require a complete re-imagining of their product lineups.

• The Rise of Electrification: We will see an even greater push towards strong hybrids, plug-in hybrids, and full battery electric vehicles (EVs). The internal combustion engine, in its pure form, may become a niche player.
• Focus on "Well-to-Wheel" Emissions: This is a game-changing concept. Instead of just measuring what comes out of your car's tailpipe (tank-to-wheel), BS7 might consider the total pollution generated, from the source of the energy all the way to the road. This means even EVs will be assessed on how the electricity that charges them is produced, pushing for greener power grids.
• New Technology and Costs: Developing vehicles that meet these ultra-strict norms will involve massive investments in research and development, which will initially impact the cost of manufacturing.

➔ For Consumers: A New Way to Drive

For you and me, the landscape of car ownership will evolve.

• A Different Kind of Car Showroom: Your choices will increasingly be between different types of electrified vehicles. The traditional petrol vs. diesel debate might become a thing of the past.
• Higher Upfront Cost, Lower Running Cost: Advanced hybrid and EV technology can be more expensive to buy. However, the long-term savings on fuel and maintenance could be significant, balancing the equation over time.
• Performance and Experience: This shift isn't a compromise. Electric motors offer instant torque, making for a surprisingly quick and smooth driving experience. The future is not just clean; it's also powerful and quiet.
• The Importance of Infrastructure: For BS7 to be a success, India's charging infrastructure needs to grow exponentially. The success of these norms will be tied to how easily you can charge your vehicle.

The journey from BS4 to BS6 was about refining a century-old technology. The journey from BS6 to BS7 will be about embracing a new one. It’s an exciting, albeit challenging, path towards a truly sustainable automotive future.
 

Expert SMC Opinions: What BS7 Could Mean for the Market

BS7 can be a complete market shift. Here's what we see coming:

• Future BS7 cars may track everything. How you drive, charge, and maintain your vehicle could directly impact your insurance costs. Safe, efficient habits might mean lower premiums.
• With bespoke BS7 components, repairs won't be simple or cheap. A minor issue might need specialized parts with long wait times. Comprehensive insurance coverage will be essential.
• A car's worth will increasingly reflect its eco-credentials.

BS7 changes everything from repairs to resale value. And at SMC Insurance, we're creating smarter insurance for this new reality.
 

Summing it all up

The journey from BS4 to BS6 was impressive, but BS7 is where things get truly exciting. This means smarter cars, greener choices, and a completely new way of thinking about driving. But more importantly, it means progress - towards cleaner air, smarter technology, and better driving experiences. And as these changes unfold, having the right protection matters more than ever. Because no matter how advanced your vehicle becomes, some things never change - like the peace of mind that comes with being properly insured.