Which engine it has decides which risk you're taking — and all of them share the fuel-tank recall.

The N Line pairs a 2.5-litre turbocharged four with an eight-speed wet dual-clutch automatic — a gearbox that is mechanically two clutches operated by computer, and new to Hyundai at the time. Recall 22V746 covers 2021 to 2022 Sonatas among others: a transmission oil-pump malfunction can impair the fail-safe limited-mobility drive mode, which can result in a complete loss of drive power. Dealers inspect and replace the transmission as necessary and update the transmission software, free. Hyundai's service bulletins fill in the picture: certain cars set high-pressure electric oil pump codes and need the whole gearbox replaced; a separate bulletin warns about moisture getting into the oil-pump connector and corroding the terminals; and a further update revises the transmission's clutch touch-point learning specifically to improve drivability and judder, with some gearboxes getting a redesigned clutch spring. An owner in our sources who has run a 2021 N Line long-term reports feeling vibration from the transmission on start-up at 15,000 miles, confirmed the recall did not apply to their build date, and says he would be concerned about how it behaves at 100,000 miles. If you want the N Line, this is the item to diligence hardest.

Two more items specific to the turbocharged 2.5. Recall 21V524 covers 2021 to 2022 Santa Fe and Sonata vehicles equipped with 2.5-litre turbocharged engines: fuel may leak at the pipe connection between the high-pressure fuel pump and the fuel rail, raising the risk of a fire. Dealers inspect and tighten or replace the pipe free, and owner letters went out in September 2021. Separately, Hyundai's bulletin describes 2.5T engines with a misassembled check valve in the PCV — the Positive Crankcase Ventilation system, which vents pressure out of the engine's crankcase — letting engine oil into the intake and contaminating the air cleaner. If a 2.5T you are looking at has an oily intake pipe or a soaked air filter, that is the bulletin to quote, not a worn engine.

The 2021's most physically alarming pattern, and it shows up on both the hybrid and the gas file. Owners describe coolant disappearing with no visible leak under the car, thick white smoke from the exhaust, no cabin heat, and eventually an overheating engine. Several name Hyundai's own bulletin. Hyundai's document covers 2020 to 2023 Sonata Hybrids and attributes it to an internal leak at the EHRS — the Exhaust Heat Recovery System, a heat exchanger built into the centre muffler that uses exhaust heat to warm the engine up faster — with supporting software updates for coolant flow and air bubbles in the system. The complaint file shows repeat failures: one owner reports a second EHRS failure at 130,000 miles, another had the repair done and the leak return. Ask directly whether the car has ever lost coolant, blown white smoke, or had a muffler or heat-recovery assembly replaced, and check the coolant reservoir level yourself.

The 2021 Sonata Hybrid draws 52 complaints, the largest hybrid file in the generation, and this is most of it. Owners report the car dead after sitting — sometimes after only a couple of days, sometimes overnight — needing the emergency key blade to get in and the dashboard 12-volt reset button to start. Some report it happening while driving, with a "Check Hybrid System" warning and a total loss of power on a busy road. Dealers frequently cannot reproduce it. Hyundai's bulletin describes diagnostic code P1BB20, 12V Lithium Battery Cell Voltage High, on Elantra, Sonata and Tucson hybrids of this era, causing a warning light and in some cases limp mode, with a Battery Management System software update as the fix. Ask whether that update has been applied, and treat a car that still dies after it as a walk-away.

Recall 21V00M covers 2020 to 2021 Santa Fe and 2021 Sonata and Elantra vehicles: during manufacturing the windshield may not have been properly bonded to the body, allowing it to detach in a crash — which matters both for occupant retention and because the passenger airbag pushes against the glass when it deploys. Dealers remove and reinstall the windshield free. Owner letters went out in June 2022. Worth confirming by VIN, and worth noting that a car whose windshield has since been replaced by a glass shop is a separate question — ask who did it.

Hyundai's bulletin is specific: certain 2020 to 2021 Sonatas with the 1.6-litre turbo engine may show a check-engine light together with a popping noise, an abnormal smell from the engine compartment, rough running or reduced power, all caused by a misfire. A separate bulletin covers repairing poor pin tension at a joint connector on 1.6 turbo-GDI cars. If a 2021 you are looking at has the 1.6T, drive it hard from low revs, listen for popping, and get any stored codes read before you buy.

The naturally aspirated 2.5-litre Theta III is the least eventful powertrain in the 2021 range. Its bulletins in this year cover mass-airflow plausibility codes and a joint-connector pin-tension repair rather than any failure of substance, and the injector problem that shows up on the 2022 and 2023 cars is only just beginning to appear. That leaves the shared fuel-tank recall and normal used-car diligence. If you want a 2021 Sonata and do not need the performance, this is the version with the shortest list.