SAIPA M15 / M16

Saipa's own petrol fours — the 1.5 M15 and 1.6 M16 — in the Quick, Shahin, Atlas and Aria.

They are among the commonest engines on Iranian roads and are essentially undocumented in English, which is the practical constraint on working on one: search the engine code rather than the model, and expect the useful material to be in Persian.

They descend from Saipa's licence-built Kia and Renault engines rather than from a clean sheet, which is worth knowing when parts are being sourced.

They are conventional port-injected fours — chain or belt by variant — and their complaints are the ordinary ones: a carboned throttle body giving a hunting idle, ignition coils, and a coolant temperature sensor that ruins economy quietly.

Fuel quality is the variable that decides an engine's life in the markets these are sold in, more than mileage does — carbon in the head and on the valves is a routine finding rather than a fault, and it responds to cleaning.