Hyundai The 2.5-liter inline four-cylinder engine is one of the most popular mills in the Hyundai Smartstream family of engines, powering a number of Hyundai vehicles, including the Hyundai Sonata, Santa Fe, Tucson, along with certain Kia and Genesis models like the Genesis GV80, Kia Sportage, Sorento, and K5. It is available in naturally aspirated, turbocharged, and hybridized forms and is capable of delivering between 187 to 300 horsepower depending on the car model. When Jalopnik tested the Santa Fe with the 277-hp turbocharged Smartstream gasoline 2.5 engine, it found it to be particularly sprightly in combination with the eight-speed dual-clutch automatic transmission in both on-road and off-road scenarios. But is it reliable? It's a question you're probably asking if you're someone who owns a Hyundai, Kia, or Genesis fitted with this engine, or is considering buying one. Well, since the engine only came out in 2019 as a replacement for the older 2.4-liter Theta II engine, definitive long-term reliability data is still emerging. However, initial reports suggest there's a reliability improvement over the problematic Theta II engines whose connecting rod bearings have been known to fail. Also, feedback from owners show that with regular servicing and maintenance, the engine should offer you years of faithful service, with some reporting that their Smartstream 2.5-liter-powered cars have gone past 150,000 miles without issues. But while many people have had no qualms with the reliability of the Hyundai Smartstream 2.5-liter engine, issues such as carbon buildup and excessive oil consumption have come up again and again, so they're worth keeping in mind. Some early production Smartstream 2.5 engines are known for excessive oil use Hyundai The biggest issue facing owners of the Hyundai Smartstream 2.5-liter engines is that certain versions produced from the 2021 to early 2023 are susceptible to abnormally high oil consumption, with some said to use up as much as one quart per 1,000 miles or less. The problem is related to the piston rings. They have a design that can compromise the internal seal between the piston and the cylinder wall, resulting in engine oil leaking into the combustion chamber, where it burns along with the air-fuel mixture. To make matters worse, carbon deposits can accumulate on the piston crown and the ring land as things further deteriorate. This can manifest in engine misfires, knocking, loss of power, and high fuel consumption. Thankfully, with the piston and ring reportedly redesigned following a mid-2023 update, oil consumption and piston-related problems should be less of an issue on 2024 and newer models. However, the direct-injected nature of the engine means that some degree of carbon buildup on the intake valves is likely to become an issue once the Hyundai 2.5-liter inline four-cylinder is nearing around 100,000 miles. Carbon buildup is known to be an especially common issue in some Smartstream 2.5-liter engines produced between 10/22/2019 and 10/01/2020 for the 2020-2021 Hyundai Sonata and other models. This is because the Exhaust Gas Recirculation (EGR) valve, which routes some exhaust gases back into the intake to reduce NOx emissions and keep the engine running efficiently, can get clogged with carbon. This causes the EGR valve to fail, resulting in rough idling, hesitation and poor engine performance. Injector leaking issues are a major reliability worry for certain owners Kia Some naturally aspirated Smartstream 2.5 engines also suffer faults with fuel injectors. The root cause is due to a factory defect that causes the injectors to leak fuel into the cylinder, which in turn upsets the delivery of the intended air-fuel mixture. When this kind of failure happens, your car will stall, hesitate, or suddenly lose power when you accelerate or while driving. Vehicles with the faulty batch of injectors include the 2020-2023 Sonata models, 2021-2023 Santa Fe, 2021-2023 Sorento, 2022-2024 Tucson, and 2023-2024 Kia Sportage. Aside from the injector issues, our understanding is that owners have had other problems with the Hyundai Smartstream 2.5-liter engine, one of which involves 2025-2026 Santa Fe, Tucson, Sorento, and K4 models manufactured between February 18, 2025 and August 8, 2025. These vehicles were recalled back in 2025 after it was discovered that they did not have their connecting rod bolts tightened enough. Left unattended, loose connecting rod bolts can lead to stalling, a knocking noise, or a very costly engine damage if the bolts fail completely, as it can cause the engine to seize. Similarly, some 2024-2025 Hyundai Santa Fe models equipped with the Smartstream 2.5 turbocharged engine were recalled due to incorrectly installed starter motor positive terminal cover, which poses a fire risk in the event of an accident. There have also been reports of some 2.5 Smartstream engines shipping with a faulty Integrated Thermal Management Modules (ITMM), which can fail completely after as little as 30,000 miles, resulting in severe engine overheating and potentially, warped cylinder head.
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