Gamma Engines (Gamma - 1.6L): Used in Accent, Rio, Elantra, and Cerato. Very practical, economical, and durable engines. Nu Engines (Nu - 2.0L): Found in Elantra, Cerato, Tucson, and Sportage. The MPI version is excellent, while the GDI has many issues. Theta Engines (Theta - 2.4L / 2.0T): Famous in Sonata, Optima, Santa Fe, and Sportage. (Note: Models from 2011 to 2019 globally suffered from manufacturing defects in the connecting rod bearings, leading to oil mixing or sudden engine damage, so be sure to inspect them carefully before buying). Smartstream Engines (Smartstream): The modern generation (from 2020 onwards), where the company focused on fixing previous generation defects and improving engine cooling.