Hyundai Nu

The 1.8 and 2.0 litre petrol four that sits between the Gamma and the Theta in the Hyundai Motor Group's range — the volume engine of the Elantra, i30, Cee'd, Tucson and Sportage through the 2010s, in both port-injected and GDI forms.

It is worth distinguishing carefully from the Theta II, because the Theta's connecting-rod bearing failures and the recalls attached to them do not apply to the Nu. Searches for "Hyundai 2.0 engine failure" return Theta material almost exclusively, and applying it to a Nu overstates the risk substantially. Confirm the engine code before repeating any of it to an owner.

The Nu's own themes are milder: intake-valve carbon on GDI versions, timing-chain noise at high mileage, and — on some build ranges — oil consumption. As with the Gamma, knock complaints in markets with variable fuel quality are worth reading as fuel before as hardware.