Kia and Hyundai are separate brands that draw on the same engine families, and two of those shared designs, the Theta II and the Nu, now sit under extended 15-year, 150,000-mile engine warranties for vehicles covered by a class-action settlement. A Kia Sportage and a Hyundai Tucson can therefore carry closely related four-cylinders under different badges.
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The overlap goes back to 1997, when Kia went bankrupt and Hyundai bought a 51% stake in it. Since then the two companies have split development and manufacturing costs on powertrains instead of running parallel supply chains, which is efficient when an engine works and awkward when one does not, because a flaw in a shared design tends to appear in the lineups of both brands at the same time and draws recalls and lawsuits that cross the corporate line.
Which engines the two brands share
Carscoops’ engine-sharing guide catalogs the overlap. The 2.2-liter CRDi turbodiesel has been used since 2009 in the Hyundai Santa Fe and Kia Sorento, and also appears in the Palisade, Sonata and Kia Carnival. A Smartstream turbo 2.0-liter four-cylinder serves the Santa Fe, Sonata and K5, mostly in Asian markets, while the Smartstream turbo 2.5-liter powers the Sonata N Line, the Kia Sorento and several Genesis models. The Smartstream G3.5 turbo V6 is shared by both brands, with Hyundai building a twin-turbo version for Genesis.
North American buyers see a narrower set. Carscoops lists the Smartstream G2.5GDi and T-GDi, the G1.6 T-GDi and the G2.0 Atkinson as the U.S.-built engines, found in the Kia Telluride and Sportage and the Hyundai Tucson, Santa Cruz and Santa Fe. The guide’s point is that a problem in one family can reach several models from both brands at once.
Theta II and Nu: the recalls and the federal penalty
The Theta II comes as a 1.8, 2.0 or 2.4-liter four-cylinder, and the Nu as a 1.8 or 2.0. Carscoops ties both families to several recalls and a large U.S. class action over reports of stalling, seizing and fires, and names among the affected vehicles the 2011-2015 Sonata Hybrid, 2014-2021 Tucson, 2011-2016 Optima Hybrid and 2011-2013 Sportage.
Regulators got involved first. On November 27, 2020, NHTSA announced consent orders requiring Hyundai and Kia to pay a combined $210 million. The agency found that the companies had conducted untimely recalls of more than 1.6 million vehicles with Theta II engines and had inaccurately reported certain information about them. NHTSA Deputy Administrator James Owens said manufacturers must appropriately recognize the urgency of their safety recall responsibilities.
Hyundai’s share was $140 million and Kia’s $70 million, each split among an upfront payment, spending on specified safety measures and a deferred penalty that comes due only if conditions are not met. Both companies also agreed to build up safety functions in the U.S., including a Chief Safety Officer at Kia and a test facility for Hyundai.
The 15-year, 150,000-mile terms and their limits
The warranty extension traces to the private litigation. Kia America’s September 26, 2022 announcement describes a settlement in In re: Hyundai and Kia Engine Litigation II, filed in the Central District of California as case 8:18-cv-02223. It covers 2.4-liter Theta II, 2.0-liter Nu and 1.6-liter Gamma engines in roughly 2.21 million vehicles, about 1.16 million of them Kia and 1.05 million Hyundai.
Standard engine coverage on these brands is 10 years or 100,000 miles. For qualifying vehicles the settlement raised that to 15 years or 150,000 miles, and ClassAction.org’s summary says the extension covers damage from connecting rod bearing failure. Owners also received cash reimbursement for certain past repairs, towing and rental costs, plus goodwill payments in specific circumstances, and a free Knock Sensor Detection System software update that watches for vibration patterns that can precede engine failure.
The extension is conditional. The ClassAction.org summary says the software update had to be done within 150 days of notice to qualify for extended-warranty repairs, and Carscoops reported in June 2024 that owners who received the update before November 4, 2023 got the longer powertrain coverage, with claims due by July 8, 2024. A Theta II or Nu engine outside the covered model years, or in a car that never got the update, is not automatically under the 15-year terms.
Kia’s announcement lists the covered models in detail. On the Kia side they include the 2011-2020 Optima Hybrid, 2017-2020 Optima Plug-in Hybrid, 2011-2013 Sorento and Sportage, 2010-2018 Forte, 2010-2016 Forte Koup and 2012-2019 Soul. Hyundai’s list includes the 2011-2019 Sonata Hybrid, 2010-2012 Santa Fe, 2010-2021 Tucson, 2014-2016 Elantra, 2014-2020 Elantra GT and 2012-2017 Veloster. A shopper looking at any of them needs the vehicle identification number checked, because coverage turns on the individual car.
One gap remains in the public record. The announcement names the 2.4-liter Theta II, 2.0-liter Nu and 1.6-liter Gamma engines, and says nothing about the 1.8-liter versions of the Theta II and Nu described by Carscoops, or about the newer Smartstream engines now sold in the same showrooms.
This article was produced with the assistance of AI and reviewed by Morning Overview editors prior to publication.
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