Toyota 8AR-FTS

Toyota's 2.0-litre turbocharged four — the company's first mainstream downsized turbo petrol, fitted to the Lexus NX 200t/300 and RX 200t/300 and to the Highlander in some markets.

Its distinguishing feature is the combination of port and direct injection (D-4ST) with a water-cooled integrated exhaust manifold, and the port injectors matter diagnostically: they wash the intake valves, so the carbon accumulation that defines most direct-injection turbo fours does not occur here in the way it does on a European equivalent. A rough-running complaint should not be attributed to valve deposits by analogy.

The engine also runs an Atkinson-like cycle at light load, switching to Otto under boost, which makes its part-load fuel trims read differently from a conventional turbo four. It has no widely documented systemic failure, so a fault on one is more likely to be genuinely individual than a known pattern.