Hyundai Smartstream G (1.0–3.5)

The Hyundai Motor Group's current petrol family, replacing the Gamma, Nu and Theta across the range — fitted to the Tucson, Sportage, Elantra, i30, Kona and Ceed, in naturally aspirated and turbocharged forms.

Its headline technology is CVVD, continuously variable valve duration — the ability to vary how long a valve stays open independently of when it opens, which no volume manufacturer had put into production before. It lets the engine move between Otto and Atkinson-like behaviour according to load.

That is diagnostically relevant in a specific way: the engine's part-load behaviour and fuel trims will not read like a conventional four, and a driveability complaint interpreted against Gamma or Nu expectations can mislead. Being recent, its long-term failure patterns are not established — which is worth stating plainly rather than assuming the Theta's bearing history transfers, because it is a different design and it does not.

⚑ Smartstream G is Hyundai.s whole current petrol range, not one engine — fourteen models here carry it at 1.0, 1.4, 1.5, 1.6, 2.0, 2.5 and 3.5 litres, from a three-cylinder turbo to a V6. Nothing generalises across it except the naming: a complaint about a Smartstream has to say which.