If you’re reading this, you’re probably considering purchasing (or currently own) a Hyundai Motor Company vehicle with the recently-introduced 2.5L Smartstream I-4 engine. If you want to learn more about its growing reputation for excessive oil consumption, keep reading.
What is the Smartstream Engine? Since its inception in 2018 and debuting in the third-generation Hyundai i30, the Hyundai Smartstream engine is a new branding of inline-three, four, six, and V6 engines available in a variety of displacements ranging from 1.0 to 3.5-liters, naturally aspirated or turbocharged, and power a multitude of Hyundai (and Hyundai’s subsidiary, Genesis), and Kia vehicles in the United States and worldwide. Depending on the variant, the Smartstream engine series is available in unleaded gasoline, diesel, and Liquid Petroleum Gas (LPG). These new engines replace the company’s Kappa, Gamma, Nu, Theta, and Lambda engines, among others. In this article, I’ll specifically discuss this engine's 2.5L naturally aspirated GDI variant because of its greater prevalence. What is the issue? Despite its recent introduction, the 2.5L Smartstream and its variants are gaining a track record of burning excessive oil. According to an excellent video translated by a member of the forum Grassroots Motorsports, the 2.5L is already being recalled in Korea because of this oil consumption problem, leading to eventual complete engine failure. I’ve posted the link to this forum post under the “Additional Resources” section of this article (and encourage you to read it yourself), but I’ll summarize what is said: The engine is designed to tolerate extremely high combustion temperatures under specific conditions for dual-injected variants of this engine that utilize Gasoline Direction Injection (GDI) and Multi-Port Fuel Injection (MPI). To manage this heat, Smartstream piston rings are nearly twice the usual ring gap found in earlier engines produced by the company. This configuration results in a significant amount of blowby. It's possible that the lower compression turbocharged version of the 2.5L doesn’t reach such high temperatures at light loads; thus, it is designed to have less of a ring gap and could improve reliability, but this is a maybe. Because of the excessive blowby, this engine’s Positive Crankcase Ventilation (PCV) system could be inadequately designed, as it fails to capture and redirect sufficient oil vapor back into the sump. Another problematic aspect is the piston design (which I believe causes many problems plaguing the company’s Nu engine, such as the one found in my 2019 Tucson), which is short piston skirts. This design promotes piston rocking within the bore, resulting in scuffing and widening tolerances. Because of the poorly designed pistons, excessive carbon and sludge can build up, exacerbated by the inadequate PCV system. As a result, this sludge only amplifies issues with the already defective piston ring design and can occur at extremely low mileage. Furthermore, sludge can accumulate on the engine’s GDI fuel injectors, affecting the fuel’s precision and likelihood of the intended "hot cycle," which is crucial for managing the wider ring gaps. In the end, the most likely culprit causing the 2.5L, and possibly other Smartstream engine variants, is the pistons' design. Interestingly, at least in South Korea, dealers attempt to mask this problem by replacing the oil dipsticks with dipsticks that lower the “normal” oil level. What should I do if I own or want to buy a vehicle that has this engine? Currently, there doesn’t seem to be a solution to prevent this oil consumption and other issues this engine will likely experience, as the root cause stems from a design flaw. For those who recently purchased a new 2.5 Hyundai/Kia, adhering to a more frequent 3,000-mile oil change interval may be the best action to take while awaiting inevitable recalls. Should I buy a vehicle with this engine? If you own the 2.5L engine, I believe it’s not a question of if it will begin burning oil but when. Unless Hyundai issues a recall that will replace 2.5L engines with updated designs, I would avoid this engine and most Smartstream engines, if not all. In short, it’s (sadly) probably in your best interest to avoid purchasing any Hyundai Motor Company vehicle unless it’s electric (though electric cars can have a host of other frustrating problems). If you own the 2.5L engine, it’s a good idea to change the oil more frequently, even as much as every 3,000 miles, especially if your goal is to keep the vehicle for a while. Opinion As many agree, I believe the uprising of problems involving internal combustion engines in today’s cars is primarily attributed to automakers wanting to squeeze out the best fuel economy possible, even if it means sacrificing reliability. Due to strict emission regulations, automakers have become desperate to find a way to make their engines as fuel-efficient as possible, but this almost always results in lowered reliability due to the effect on the engine itself. Ironically, excessive oil consumption can increase emissions, undermining the environmental benefits the engine was designed to have in the first place. I personally have no tolerance for excessive oil consumption with my cars, even slight oil consumption for that matter (and so far, none of them exhibit it). Automakers will tell you oil consumption is normal (i.e., one quart every 1,000 miles), but the reality is it is not normal, and that should not be happening if the compression ratios, tolerances, and piston designs are designed appropriately. If one or the other is too great, problems will arise eventually. One of the saddest aspects about this issue is that the Smartstream engine series, at least in my eyes, is Hyundai’s attempt at a fresh start—to get away from the bad publicity and endless problems plaguing their former engines, most notably the horrendous Theta II and Nu I-4s. In an ideal world, engines should be designed around reliability over fuel economy, not the other way around, but regulations have forced it to be this way, which is usually not in the consumer’s best interest. Hyundai could have designed the 2.5L and likely other Smartstream engines to be more durable, but they chose not to. Unfortunately, Hyundai has not learned from its prior mistakes, and another decade of bad reputation may be underway. Additional resources Hyundai/Kia Smartstream Problems - Additional Information Now you know the truth behind Hyundai’s 2.5L Smartstream I-4 engine and its issue with consuming excessive amounts of oil. I hope you have found this information informative and helpful. Still have questions or comments about this issue? I'd love to help. Feel free to leave them in the comments section below.
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AuthorRyan Emery is an avid automotive enthusiast, researcher, and investigator specializing in defect analysis and recalls. |