BS4 petrol engine: what you need to know

India moved to BS4 (Bharat Stage 4) standards to cut pollution and improve fuel use. If you’re eyeing a car or bike with a BS4 petrol engine, you’ll want to know how it differs from older models and what to look out for. Below we break down the key specs, why the standards matter, and simple steps to keep the engine healthy.

Core specs and performance

BS4 engines usually have a tighter fuel‑air mix, thanks to better injectors and a more precise ECU. That means you’ll see a modest boost in power – often 5‑10% more than a similar BS3 unit – while sipping a little less fuel. Expect a mileage improvement of around 3‑6 km per litre, depending on driving style.

Emission limits are stricter too. The carbon monoxide (CO) cap drops to 1.5 g/km, hydrocarbons (HC) to 0.2 g/km, and nitrogen oxides (NOx) to 0.25 g/km. To meet these numbers, manufacturers add catalytic converters and exhaust gas recirculation (EGR) systems. These parts add a bit of weight but keep the engine cleaner.

Buying tips for a BS4 petrol engine

When you shop, check the model’s certification label – it should say ‘BS4’ clearly. Look for a clear service history; a well‑maintained BS4 engine stays within its emission limits longer. Ask about the warranty on the catalytic converter – it’s a pricey component that can fail if the engine runs too hot.

Fuel quality matters. BS4 engines are tuned for low‑sulphur petrol (≤10 ppm). Using higher sulphur fuel can poison the catalyst and raise emissions. Stick to reputable fuel stations and avoid “cheap” pumps that might cut corners.

Don’t ignore the air filter. A clogged filter forces the engine to work harder, hurting both fuel economy and emissions. Replace it every 12‑15 000 km or sooner if you drive in dusty conditions.

Finally, think about future regulations. BS6 standards are already rolling out in many cities, and some older BS4 vehicles may face restrictions in low‑emission zones. If you plan to keep the vehicle for several years, consider how soon you might need an upgrade.

Keeping a BS4 petrol engine running smooth is mostly about regular care. Change oil on schedule, use the recommended grade, and keep an eye on coolant levels. Follow the manufacturer’s service intervals and run a diagnostic scan once a year to catch any sensor glitches early.

In short, BS4 petrol engines offer a good balance of power, fuel savings, and cleaner exhaust. By checking certification, using quality fuel, and staying on top of maintenance, you can enjoy those benefits without surprise breakdowns. Happy driving!