Between 2011 and 2019 Hyundai and Kia sold several million cars in the United States with a family of four-cylinder engines called Theta II — a 2.4-litre naturally aspirated unit and a 2.0-litre turbocharged one. A proportion of those engines fail. Metal debris left in the crankshaft passages during manufacturing restricts oil flow to the connecting-rod bearings; the bearings wear, the engine begins to knock, and if it is driven on it can seize or throw a rod through the block, sometimes with a fire. The first recall came in 2015, the second in 2017, and the regulator's investigation into whether the companies had recalled promptly enough ended in 2020 with a civil penalty of 210 million dollars and an agreement to extend the engine warranty to fifteen years and unlimited mileage for the affected cars.
That history is why six nameplates from these two companies sit in the bottom quarter of this site's scores for 2011 to 2017, and why the same nameplates from 2018 onward sit in the top quarter.
The cars
The recall covers, broadly, these model years with the 2.0-litre turbo or the 2.4-litre Theta II engine:
- Hyundai Sonata 2011 to 2019 (the 2011 model year alone has more than 3,300 complaints on record)
- Hyundai Santa Fe and Santa Fe Sport 2013 to 2019
- Hyundai Tucson 2014 to 2019 (2.0 and 2.4-litre only)
- Kia Optima 2011 to 2019
- Kia Sorento 2011 to 2019
- Kia Sportage 2011 to 2019
Later campaigns extended similar treatment to the smaller Gamma and Nu engines in the Kia Soul, Kia Forte, Hyundai Elantra, Hyundai Veloster and Hyundai Kona for certain years, mainly for a different failure — catalytic-converter damage leading to piston failure — under a separate recall in 2019 and 2020. The Elantra and Soul pages on this site show that pattern at a lower level.
Hyundai Sonata: the record, year by year
| Year | Score | Verdict | NHTSA complaints | Recalls |
|---|---|---|---|---|
| 2025 | 90 | BUY | 16 | 0 |
| 2024 | 88 | BUY | 45 | 1 |
| 2023 | 87 | BUY | 87 | 2 |
| 2022 | 84 | BUY | 93 | 3 |
| 2021 | 83 | BUY | 130 | 4 |
| 2020 | 82 | BUY | 175 | 4 |
| 2019 | 91 | BUY | 160 | 0 |
| 2018 | 82 | BUY | 372 | 1 |
| 2017 | 56 | CAUTION | 763 | 3 |
| 2016 | 54 | CAUTION | 723 | 6 |
| 2015 | 28 | AVOID | 1,144 | 9 |
| 2014 | 59 | CAUTION | 746 | 7 |
| 2013 | 25 | AVOID | 1,908 | 9 |
| 2012 | 28 | AVOID | 1,556 | 8 |
| 2011 | 24 | AVOID | 3,374 | 12 |
Live from the federal record as of 2026-10-04; linked years have their own page. Full table and repair costs on the Hyundai Sonata model page.
Kia Optima: the record, year by year
| Year | Score | Verdict | NHTSA complaints | Recalls |
|---|---|---|---|---|
| 2020 | 91 | BUY | 145 | 0 |
| 2019 | 89 | BUY | 206 | 1 |
| 2018 | 89 | BUY | 232 | 2 |
| 2017 | 86 | BUY | 255 | 3 |
| 2016 | 53 | CAUTION | 754 | 5 |
| 2015 | 42 | AVOID | 1,007 | 4 |
| 2014 | 61 | CAUTION | 585 | 7 |
| 2013 | 26 | AVOID | 1,381 | 9 |
| 2012 | 58 | CAUTION | 919 | 5 |
| 2011 | 73 | BUY | 593 | 5 |
Live from the federal record as of 2026-10-04; linked years have their own page. Full table and repair costs on the Kia Optima model page.
What the fix actually is
There is no recall that replaces every affected engine. The recall remedy is an inspection and a software update: the Knock Sensor Detection System, which listens for the bearing knock and, if it hears it, puts the car into a reduced-power mode and lights a warning so the owner can get to a dealer before the engine destroys itself. An engine that is already knocking at inspection is replaced under warranty. An engine that passes gets the software, the extended warranty, and a note in the dealer's system.
That means a used car from these years falls into one of three groups. It has had a replacement engine, which is the best outcome — the replacement blocks are cleaned properly and the failure rate on them is low. It has passed inspection and had the software installed, which means it is protected against a catastrophic failure but may still fail and need the engine replaced later, under the extended warranty if that warranty transfers. Or it has had nothing done, which is the case to avoid.
How to tell which group a car is in
Check the VIN at nhtsa.gov/recalls: an outstanding engine recall shows there. Then ask the seller, or the dealer's service department, for the campaign history: a completed knock-sensor update appears as a campaign number, and a replaced engine appears as a warranty engine replacement with a date and mileage. Confirm that the fifteen-year, unlimited-mileage engine warranty applies to the car; it was extended to original and subsequent owners for the recalled vehicles, but the terms vary by campaign, and a dealer can check the specific VIN.
On the test drive, start the engine cold and listen for a metallic knock that rises with engine speed. Check the oil level; a low level on an engine that has not been serviced recently is a warning, because bearing wear and oil consumption go together on these engines. A check-engine light with the car in reduced power is the knock sensor doing its job — walk away or price the car for an engine.
The other side of the ledger
The same companies' cars from 2018 onward have some of the best records on this site. The 2019 to 2025 Sonata scores between 83 and 92; the 2018 to 2020 Optima between 86 and 92; the 2020 Sorento 91. The engines were reworked, the cleaning process fixed, and the fleet on the road had been through two recall campaigns. A shopper who rules out Hyundai and Kia because of the recall is ruling out some of the most dependable cars of the past five years. A shopper who ignores the recall on a 2011 to 2017 car is buying an engine with a known failure mode and no proof it has been addressed.
Summary
Avoid, or buy only with a replaced engine and documentation: 2011 to 2017 Sonata, Optima, Sorento, Santa Fe, Sportage and Tucson with the 2.0 turbo or 2.4-litre engine. Buy with confidence: the same nameplates from 2018 or 2019 onward.