Skip the 2016 and 2017 — those are the engine years. Hunt for the 2019 or the 2023.

The engine the Sonata is famous for. The volume engine through 2019: a 2.4-litre four with GDI, meaning Gasoline Direct Injection. Its failure is the connecting-rod bearings — the metal shells the piston rods spin on — wearing early, and it announces itself in a fixed order: oil consumption creeps up, a deep knock appears, then the engine seizes or shuts off at speed. Hyundai's answer has two halves. Service Campaign 966 installs KSDS, the Knock Sensor Detection System, software that listens for the vibration of early bearing wear, flashes the warning light and puts the engine into a protection mode; the diagnostic code is P1326. Separately, Hyundai extended the warranty on the engine long block for rod-bearing damage in stages — 10 years/120,000 miles, then 15 years/150,000 miles, then a Limited Lifetime Warranty, valid for the original and subsequent owners. Confirm which tier applies to a VIN with Hyundai. Note that on the gas car this is a campaign and a warranty, not a safety recall.

Same bearings, three extra parts. The 2.0-litre turbocharged member of the same Theta II family, fitted to the Sport and Limited trims. Hyundai's knock-sensor campaign and rod-bearing warranty extension name it alongside the 2.4, so the bearing story and the coverage are identical. What is different is what the turbo adds. Hyundai's bulletin describes the air inlet hose near the turbo inlet deteriorating, causing an air-rushing noise and possible turbocharger damage, with a service campaign to replace it on 2015 to 2017 cars. An independent mechanic adds two more from the workshop floor: the electronic wastegate actuator that controls boost is a common failure point, and the electric vacuum pump that assists the brakes can fail and take down the car's communication network, lighting the whole dashboard. His summary is fair — more fun, more complexity.

The Eco trim a mechanic tells you to walk away from. The 1.6-litre turbo Eco pairs with a seven-speed dual-clutch transmission — mechanically a manual gearbox operated by computer, which is why it behaves oddly at crawling speed. The independent mechanic in our sources is unusually direct about it: don't buy one, the dual clutches in these are absolutely terrible, they shift badly, and there was often nothing he could do because that was simply how they were built. Hyundai issued engine- and transmission-control software updates for shift quality on 2015 to 2017 cars. This trim also runs a manually adjusted alternator belt whose top mounting bolt can break if overtightened, which lights the battery warning and in some cases overheats the engine — there was a service campaign for that too. If you want a seventh-generation Sonata, the 2.4 with the conventional six-speed automatic is the far easier ownership proposition.

The two versions that got real engine recalls. The seventh-generation hybrid and plug-in are the only Sonatas with a safety recall for the bearing problem — 20V746 on the 2016 hybrid and 21V727 on the 2017 hybrid, both of which inspect the engine, replace it free if bearing damage is found, and install the knock-sensor software. Their own complaint files add a second fault entirely: a "Check Hybrid System, turn off engine" warning followed by total loss of motive power, sometimes at highway speed, often with the car shaking. The plug-in's version of that is a failed high-voltage battery, and owners report waiting a year or more for a replacement. The plug-in was also left out of 21V727, which one owner discovered when their engine developed a hole in the block at 76,000 miles. Confirm the applicable recall by VIN and ask for the battery's history.

The redesign's base engine — and its injectors. A 2.5-litre direct-injection four, new for 2020 and unrelated to the old Theta II despite the family name. It has no bearing story. Its recurring fault is in the fuel injectors: Hyundai's bulletin states that the injectors leak internally because the filter inside them breaks apart, producing misfire codes, and instructs dealers to replace all four rather than the failed one. That bulletin covers 2021 to 2023, and 2023 owners describe the consequence — losing power at highway speed, sputtering at a stoplight, jerky acceleration with a check-engine light, and in some cases a second failure a year later. One owner's dealer confirmed a bad injector leaching gasoline into the engine oil. On cars this age it is usually a warranty repair, so ask whether it has been done rather than find out later.

The N Line's gearbox is the risk, not the engine. The N Line pairs a 2.5-litre turbo with an eight-speed wet dual-clutch automatic that was new to Hyundai at the time. Recall 22V746 covers 2021 to 2022 cars: a transmission oil-pump malfunction can impair the fail-safe limited-mobility mode and cause a complete loss of drive power, and dealers replace the transmission as necessary. Hyundai's bulletins fill it in — cars setting high-pressure electric oil pump codes may need the whole gearbox, moisture in the oil-pump connector corrodes the terminals, and a later software update revises clutch touch-point learning specifically to improve judder, with some gearboxes getting a redesigned clutch spring. Recall 21V524 separately covers a fuel leak at the high-pressure pump connection on 2.5-litre turbo cars. A long-term N Line owner in our sources reports transmission vibration at 15,000 miles and says he would be concerned about 100,000.

The mid-trim turbo with a specific misfire. For 2020 and 2021 the upper gas trims used a 1.6-litre turbo instead of the 2.5 — a substitution one reviewer in our sources objects to directly, arguing the naturally aspirated engine further down the range is the better choice. Hyundai's bulletin names the fault to listen for: certain 2020 to 2021 Sonatas with the 1.6T may show a check-engine light together with a popping noise, an abnormal smell from the engine compartment, rough running or reduced power, all from a misfire. A separate bulletin covers repairing poor pin tension at a joint connector on 1.6 turbo-GDI cars. A federal complaint describes exactly the symptom — loud explosive popping while driving. Accelerate hard from low revs on the test drive and have any stored codes read.

Two faults, two bulletins, and they account for nearly the whole file. The 2020 to 2023 hybrid has almost no engine complaints and two electrical-and-cooling ones that repeat relentlessly. First, the 12-volt battery going flat while the car sits — owners unlock with the emergency key blade and press the dashboard 12V reset button, sometimes weekly, with dealers unable to reproduce it; Hyundai's bulletin describes diagnostic code P1BB20, 12V Lithium Battery Cell Voltage High, causing a warning light and in some cases limp mode, fixed by a Battery Management System software update. Second, coolant disappearing with thick white smoke from the exhaust and the engine overheating; Hyundai's bulletin attributes this on 2020 to 2023 Sonata Hybrids to an internal leak at the EHRS, the Exhaust Heat Recovery System built into the centre muffler, which uses exhaust heat to warm the engine up faster. Both are usually warranty repairs. Ask about both by name.