The rule that applies depends on your country and on what the engine is fitted to. A mobile machine, a stationary genset and a vehicle can fall under different rules even in the same country.
The legal responsibility usually sits with the engine manufacturer for certification and with the importer for placing a compliant product on the market. Always confirm the current rule with your regulator or a specialist adviser before you order.
The main regimes, as of October 2026
- European Union: non-road engines fall under Regulation (EU) 2016/1628, known as Stage V. It covers diesel engines across power bands, and for engines between 19 and 560 kW it sets a particle number limit that in practice requires a diesel particulate filter.
- United States: new non-road diesel engines must meet EPA Tier 4 standards under 40 CFR Part 1039 and be covered by an EPA certificate of conformity to be imported. Stationary engines are covered by separate EPA rules, and California adds its own requirements.
- Great Britain: the EU non-road regulation was kept in domestic law after Brexit. Check the current approval route with the UK authorities.
- India: gensets up to 800 kW must meet the CPCB IV+ limits notified in November 2022, which took effect from 1 July 2023. This matters if you buy gensets also sold in India.
Other markets
Many other countries either adopt EU or US limits by reference or have no rules for small stationary engines. Some apply rules only to engines above a set power, or only to mobile machinery. Rules also change over time, so a model that was legal to import last year may not be legal now.
Fuel rules matter too. Engines with filters and exhaust treatment usually need low-sulphur diesel. If your market's fuel is high in sulphur, a certified engine can still fail early in service.
Why small Indian engines often fall short
Most small engines from Rajkot are built for Indian farm use. Many are not type-approved for EU Stage V or certified by the EPA. A certificate applies to a specific engine family, so a factory cannot simply declare that its engine complies.
If your market requires certification, ask for the certificate itself and check that the engine family on it matches the model you are buying. Whether Indian engines can meet EU Stage V or EPA rules explains this in more detail.
How to check your own market
- Ask your national environment or transport regulator which rule covers the engine type and use.
- Ask a customs broker whether the engine needs an emission certificate at import.
- Ask your competitors' suppliers which approvals their engines carry, as a reality check.
- Write the required standard into your purchase contract, so the factory carries the risk of a wrong claim.
Next step
We check that the certificates a factory shows you are real and match the engines it ships. To review your market's requirements against a supplier's range, book a free sourcing review.