Chevrolet SGE (1.0–1.5 turbo)

General Motors' small turbocharged petrol family — 1.0 to 1.5 litres, three and four cylinders — fitted to the Cruze, Malibu, Equinox, Trax, Onix and their Buick and Opel equivalents, replacing the older Ecotec fours in the volume range.

The recurring items are those of any modern downsized turbo: intake-valve carbon on the direct-injected versions, turbocharger life tied closely to oil condition, and the plastic components of the cooling system and PCV. The PCV is worth naming specifically — a failed diaphragm in the valve cover produces a large vacuum leak that reads as a lean code and a rough idle, and the whole cover is usually the replacement part.

These engines went into cars sold heavily in markets with variable fuel quality and long service intervals, and both show up as knock and carbon complaints rather than as component failures. Fuel and oil history explain more faults here than mileage does.