If you’re reading this, you’re probably considering purchasing (or currently own) a Hyundai Motor Company vehicle with the 2.0L Nu GDI I-4 engine. If you want to learn more about a possible emerging problem, keep reading.
What is the Nu Engine? The Hyundai Nu engine is a common inline four-cylinder engine in 1.8 and 2.0-liter configurations powering several Hyundai and Kia vehicles in the United States and worldwide. It was first introduced in the 2011 model year Hyundai Elantra to replace the Beta engine series and has both MPI (multi-port injection) and GDI (gasoline direct injection) variants. In this article, I specifically want to discuss the 2.0L GDI variant because I own this engine and have over two year’s experience with it. What is the issue? Variants of the Nu engine are prone to several issues (such as bearing wear and excessive oil consumption), but in this article, I want to shed light on the GDI variant, where fuel dilutes the engine oil. This isn’t a good thing because if the ratio of fuel becomes too great compared to oil, the oil’s viscosity changes to where it can’t properly lubricate critical engine components, causing premature wear. I’ve experienced this issue with my 2019 Hyundai Tucson SUV. Owners can quickly identify if this problem is occurring by checking the engine oil level. Over time, if the level increases beyond the full mark, fuel is diluting the oil. Generally speaking, every engine will have a little bit of fuel dilution. But with modern engines today, automakers have ramped up fuel injection pressure and compression ratios, dramatically increasing the chance of this dilution occurring. What should I do if I own or want to buy a vehicle that has this engine? As of now, I’m not aware of any solution that will permanently prevent this dilution. But interestingly, when I used premium fuel in my car (91 octane) instead of 87 a few weeks ago, my oil level decreased a little shortly after. Of course, it could be a coincidence the level dropped when I put in premium fuel, but it’s worth investigating. Additionally, I have read several tips across the internet that could aid in mitigating the severity of the dilution, such as: 1. Reduce idle time Many vehicles experience the oil-fuel dilution problem, especially law enforcement and emergency service vehicles that idle for an extensive amount of time. Avoiding excessive idle time can slow down the dilution process. Note that I mention extensive idling. There are situations where some idling is necessary to allow all engine components to be adequately lubricated. Most engine wear occurs within the first 30 seconds of initial startup. An example of required idling is when you first start your car in the morning, and the engine is cold. From personal experience, I recommend letting it idle for at least three minutes before you drive off so the oil has had enough time to circulate through the engine. When you do drive off, drive lightly until the engine reaches operating temperature. If your environment is freezing, let your engine idle for several additional minutes. I also recommend you ensure the engine has reached operating temperature before performing any highway or spirited driving. 2. Use quality fuel In my view, with modern engines, the bare minimum octane you should be using is 87. Lower octane ratings such as 85 may have been acceptable for use in vehicles made more than 20 years ago that had low compression ratios, but I would never use it today. Anything lower than 87 octane has significantly less knock resistance. Over time, knocking (which is abnormal combustion) can cause catastrophic damage to the engine. If your engine’s knock sensors detect knocking, the timing of the spark plug will be altered to help prevent this additional combustion. To combat the possibility of your engine knocking, consider trying premium fuel, which is generally rated 91 octane and higher. 3. Avoid short trips When it comes to fuel dilution, driving for extended periods lets the engine remain at operating temperature long enough to burn off the remaining vapor inside. And have you ever noticed that when you start your car in the morning, you sometimes see white exhaust for a little bit? That’s your engine expelling moisture that has accumulated inside. By making constant short trips, your engine does not reach its operating temperature for very long, so not all vapor will be expelled. Driving for extended periods helps with this. 4. Don’t lug the engine This is where I mention a common culprit responsible for ruining so many of today’s modern engines: Low-Speed Preignition, or LSPI. LSPI, also known as engine knock, occurs when fuel detonates prematurely prior to the spark-triggered ignition. The spark ignition is the only ignition that’s supposed to happen. As with GDI engines, when the fuel is injected directly into the combustion chamber, it dilutes the oil film lining the cylinder that is providing needed lubrication. This fuel dilution reduces the viscosity of the oil, resulting in an oil-fuel mixture accumulating in the upper reaches of the piston. During the compression stroke, where the piston moves upward, these droplets in the combustion chamber can auto-ignite prior to the spark ignition. With LSPI, this unintended sub-combustion creates enormous additional stress within the combustion chamber and can damage pistons, connecting rods, and other components. In severe cases, LSPI will destroy the engine entirely, and a rebuild (or replacement) is required. A way to prevent LSPI is to avoid driving at low speeds with high loads. The ideal environment for LSPI to occur is maintaining an approximate RPM of 2,000 or below while driving at a high load, such as climbing long grades or towing heavy loads. For example, if you need to pass someone, don’t be afraid to downshift to a higher RPM and pass. Conversely, don’t remain in the highest possible gear and the lowest RPM and try to speed up. 5. Incorporate more highway/freeway driving Driving at higher speeds for longer periods of time is the best kind of driving for your car. Not only does it allow the engine to remain at its operating temperature, but it may help clear out some carbon deposits stuck onto the intake valves and top of the cylinder head. GDI engines are notorious for this build-up, especially on the intake valve. With enough carbon caked on the valves, engine problems can occur such as reduced performance. 6. Use high-quality engine oil and change it at shorter intervals Changing the engine oil will not necessarily prevent fuel dilution, but it is the best proactive measure to take to ensure the oil viscosity is appropriate in protecting against wear. 3,000-mile engine oil has better protection than 5,000-mile oil because oil breaks down over time, so longer intervals offer less protection. This suggestion is geared to preventing damage that can be caused by dilution reducing the oil's viscosity too much. Ideally, with modern engines, use full-synthetic. Synthetic oil is engineered in a laboratory to offer the greatest protection of wear to your engine. Also, use a thicker oil weight such as 5W-30 or 5W-40, especially if you live in a hot climate. More viscous oil will aid in cooling components, but make sure it’s not too thick. With oil that’s too thick, vital passageways can become blocked and damage components, such as variable valve timing solenoids. In general, use a thinner oil if you live in below-freezing climates for better flow properties. In my opinion, and the opinion of many Hyundai owners owning various engines the company has produced, DO NOT follow their stated oil change intervals at 7,500 miles. We strongly suggest oil changes are performed no more than 5,000 miles. In most cases, and assuming you do not live in a freezing climate, at a minimum use 5W-30 weight and not 5W-20 that’s stated on the oil cap. The 5W-20 rating is purely to satisfy federal fuel economy requirements and will boost your fuel economy by only a fraction of a mile per gallon. Choose the oil weight that best suits your environment. And regardless of automaker or engine, if you’re experiencing oil-fuel dilution, I recommend changing the oil every 3,000 miles. Above all else, Oil is cheap. Engines are not. Should I buy a vehicle with this engine? When I bought my Tucson, I wasn’t aware these engines had a predisposition to experience this issue. In fact, I didn’t know most GDI engines, in general, suffered from this. I love my car, but I’m disappointed to have this happen to a vehicle that’s so new. If you’re considering buying a Hyundai or Kia vehicle with the 2.0L GDI Nu, I’d be cautious. When looking at the car, the first thing I’d do is check the oil level. If it’s past the full mark, fuel dilution is occurring. The day I bought my Tucson, I checked the oil and noticed the level was higher than it should have been, but I assumed the dealership overfilled it. It turns out I was wrong. For now, I wouldn't advise avoiding a Hyundai or Kia vehicle with this engine purely because of this problem, but it’s essential to keep in mind. Other manufacturers are experiencing this problem, and it’s not just Hyundai. Honda has had major dilution issues with their 1.5L turbocharged engine and has issued a recall. I’ve also begun to come across reports of Toyota and Mazda four cylinders experiencing this, and I’m confident this issue will eventually affect other automakers. So far, it appears four-cylinder engines are most susceptible to fuel diluting the engine oil, likely because of their higher compression ratios. I have yet to learn of a V6 or V8 experiencing this dilution, but I’m sure examples are out there. Opinion As of now, I think it’s not a question of if fuel will begin to dilute the oil, but when. I theorize a couple of things are causing this: First, 87 octane fuel doesn’t offer adequate protection from engine knocking or LSPI. So far, I have tried 87 octane, 88 octane with no added ethanol, and most recently 91 octane. My oil level continued to gradually rise while using the 87 and 88 but decreased upon using 91. Again, this could be a coincidence, but maybe it’s not. Traditionally, high-performance engines require premium fuel because of their higher compression ratios, whereas lower performance engines can operate fine off of 87 or even 85 octane. The Nu variant in my Tucson may only have 160 horsepower, but the compression ratio is very high (being 11.5) whereas my old car, having a twenty-year-old V6, is only 9.3. Although my Tucson’s engine is not used in a Ferrari or Lamborghini, perhaps it is still considered high performance from a mechanical perspective and required premium fuel all along despite Hyundai’s 87 octane recommendation. In other words, maybe Hyundai is recommending fuel that is too low of octane than what the engine needs. Second, relating to the compression ratio, perhaps the compression is too great than what the piston rings and oil control rings are capable of handling. Maybe if the compression were lower, this problem wouldn’t exist. For fuel to mix with engine oil, it is somehow be getting past the piston rings. With the current cylinder, piston ring, and oil control ring design, the excess compression could be contributing to this. I doubt Hyundai is going to take any action, at least not any time soon. I’ve created a thread on Hyundai Forums that discusses this problem. It’s worth reading if you want to learn more about this. As I’ve mentioned, I’m experimenting with premium fuel to see if that prevents or mitigates fuel diluting engine oil. This experiment will likely be long-term, but I’ll be sure to periodically post my findings on the forum (link below). Additional resources Oil-Fuel Dilution Thread I Started on Hyundai Forums Now you know the truth behind Hyundai’s 2.0L Nu I-4 engine. 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. And if you know of any tips that could help mitigate or prevent fuel diluting engine oil, I’d love to hear them.
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AuthorRyan Emery is an avid automotive enthusiast, researcher, and investigator specializing in defect analysis and recalls. |