Best Engine Oil for Trucks & Buses in India (BS-VI)
For a commercial fleet, engine oil is a running cost and a reliability decision at the same time — the right oil protects the engine, holds up between long drain intervals, and can even save a little fuel. Here is how to choose the best engine oil for trucks and buses in India.
The common grades
Most Indian heavy-duty diesel engines run on 15W-40 — the all-round standard. 20W-40 still suits some older engines and very hot regions, while newer BS-VI engines increasingly move to lighter, fuel-efficient grades like 10W-30 or 5W-30 where the maker specifies them.
| Grade | Best for |
|---|---|
| 15W-40 | The heavy-duty standard for most trucks & buses |
| 20W-40 | Older engines, consistently hot regions |
| 10W-30 / 5W-30 | Newer BS-VI engines specifying low-viscosity oil for fuel economy |
API rating matters more on commercial engines
The API rating tells you how well the oil handles soot, heat and wear over long hours. For most trucks and buses, look for API CI-4; newer high-output and BS-VI highway engines may call for CK-4. Match the rating to the engine — a correct-viscosity oil with an outdated API rating is a false economy on a hard-worked engine.
BS-VI engines: a note on low-SAPS
BS-VI vehicles run exhaust after-treatment (DPF/SCR). Some require low-SAPS (low sulphated-ash, phosphorus, sulphur) oils to protect that hardware. Always check the handbook — using a non-specified oil in a BS-VI engine can shorten the life of expensive emissions components.
Drain intervals & fuel economy
Follow the OEM drain interval, and shorten it for stop-start city buses, overloading or dusty routes, which age oil faster. A correctly-specified oil plus clean filters is the cheapest reliability you can buy on a commercial fleet, and the right low-viscosity grade on a BS-VI engine can trim fuel use by a small but real margin across a large fleet.
Haruto for fleets
Haruto’s diesel engine oils cover the common commercial grades in bulk pack sizes, with distributor and fleet pricing — talk to us about fleet supply.