2018 Hyundai Sonata: sudden loss of power

Filed Jul 20, 2026 · Engine · TX

The lower aluminum engine oil pan developed a structural hairline fracture ("micro-crack") directly along the factory casting ridge adjacent to the drain plug. The component failed without any external impact, road hazard, scraping, or underbody damage. The failure was officially confirmed and documented by Eckert Hyundai during a service visit on July 13, 2026 (Case #42971835). Following the dealer oil service, the fracture degraded into an active, worsening oil drip that requires a catch tray under the vehicle to capture leaking fluid. The vehicle is currently available for inspection. Safety Risk: An active engine oil leak poses a significant safety hazard. Rapid or continuous loss of engine oil can cause sudden oil starvation, severe engine seizure, or total power loss without warning while driving at highway speeds, increasing the risk of a crash. Furthermore, dripping oil contacting hot exhaust or engine components presents a potential fire hazard. Prior Symptoms / History: This vehicle has a well-documented history of severe internal engine issues and thermal stress, including excessive oil consumption (running 1.2 quarts low in 1,127 miles), valve cover gasket failure, and severe drivetrain vibrations from failing front axles. The excessive internal crankcase pressure and thermal stress from these underlying defects contributed directly to the material fatigue and structural failure of this aluminum oil pan.

Filed May 6, 2026 · Engine, Fuel system · TX

I am submitting this complaint to report a serious and ongoing safety defect involving the engine of my 2018 Hyundai Sonata Sport equipped with the 2.4L Theta II engine. The vehicle has been officially tested and documented by Hyundai as consuming more than two (2) quarts of engine oil per 1,000 miles, which Hyundai has acknowledged following completion of its oil consumption test procedure. Despite this confirmation, Hyundai has declined to fully correct the defect. As the condition has progressed, the engine now fouls spark plugs every 350–500 miles, resulting in: •Engine misfires •Loss of power during operation •Rough running and hesitation •Risk of sudden engine stalls while driving This condition occurs without warning and requires repeated roadside or emergency repairs simply to keep the vehicle operable. The condition has deteriorated further, requiring replacement of fouled spark plugs every 350-500 miles. Loss of power and engine shaking can occur at any time, presenting a safety hazard for me and other drivers.

Filed May 5, 2026 · Engine · AR

Despite proper maintenance, the vehicle is burning oil at an excessive rate. I have already replaced the oil pan, but the issue persists. I now have to add oil frequently between oil changes. This creates a serious safety concern, as low oil levels can cause engine failure while driving, leading to sudden loss of power or stalling in traffic. This puts me, my passengers, and other drivers at risk. There are no visible leaks, which suggests the oil is being burned internally. This appears to be a potential defect rather than normal wear and tear. I am requesting that this issue be investigated as it may affect other vehicles of the same make and model. This is becoming very expensive having to refill oil as the dipstick shows nothing. This has been confirmed by technicians that there has been no oil in my car despite coming in on time or before the recommended miles. The oil light will come on a few weeks after having the oil changed. It seems this is an issue with this engine type.

Filed Mar 21, 2026 · Engine, Fuel system · AZ

The vehicle developed a progressive engine failure beginning in early 2024, including loud knocking noises at cold start and visible white/gray/black exhaust smoke. The condition worsened over time. In February 2026, the failure escalated to active oil discharge from the exhaust pipe while the engine was running. Oil exiting through the exhaust indicates internal engine failure (such as piston rings, cylinder walls, or valve seal failure), not an external leak. This creates a safety risk including potential loss of power while driving, risk of engine seizure, and possible fire hazard due to oil in the exhaust system. The condition has been documented on video multiple times and was shown to dealership personnel. The vehicle was taken to a Hyundai dealership for evaluation and remains available for inspection. Despite this, no written diagnostic findings or repair determination have been provided. The issue has been persistent, progressive, and reproducible, and represents a potential defect affecting engine integrity and safe operation of the vehicle.

Filed Feb 20, 2026 · Engine · CA

The component involved is the engine (2.4L Theta II gasoline engine) in my 2018 Hyundai Sonata. The malfunction involves excessive internal engine oil consumption between oil changes. The vehicle consumes oil at an abnormal rate, requiring frequent top-offs to prevent low oil levels. The vehicle is available for inspection upon request. This condition creates a safety risk because excessive oil consumption can lead to critically low oil levels, engine seizure, sudden engine stall, or loss of propulsion while driving. A sudden engine stall or loss of power while operating at highway speeds could increase the risk of a crash. The problem has been inspected and documented by an authorized Hyundai dealership. During service, the dealership recorded that the customer reported oil burning between oil changes and noted evidence of engine oil consumption. No permanent repair has been performed. The issue remains unresolved. Hyundai Motor America has not physically inspected the vehicle directly but has reviewed the case through customer care. The manufacturer has required additional diagnostic testing at the owner’s expense as a condition of further evaluation and declined to authorize testing at no cost or provide assurance of reimbursement. No crash, fire, or injury has occurred to date. The vehicle has not been inspected by police or insurance representatives. There were no warning lamps illuminated at the time the oil consumption was first observed. The condition was first noticed when oil levels were found to be significantly low between scheduled oil changes. The issue has been ongoing and progressive. Given the known history of engine-related issues involving Hyundai Theta II engines, I am submitting this complaint due to concerns that continued oil consumption may result in engine failure, sudden stall, or loss of propulsion while driving, creating a potential safety hazard. The vehicle remains in service but the condition has not been corrected.

Filed Dec 16, 2025 · Engine, Fuel system · NJ

While driving on the highway, my 2018 Hyundai Sonata experienced sudden loss of engine power and became undrivable. The failure occurred without warning at approximately 86,500 miles. At the time of the incident, there were two children in the vehicle, and the breakdown occurred at night in cold temperatures (approximately 20°F). An authorized Hyundai dealership later diagnosed zero compression in cylinder 3 and confirmed a cracked piston, recommending full engine replacement. The sudden loss of power while driving created a safety risk due to traffic conditions and environmental exposure.

Filed Nov 25, 2025 · Engine · TX

Car started misfiring while driving and engine light came on. It kept losing power but I was able to pull off highway. This put myself and others in danger because speed was significantly reduced suddenly. Dealer said problem was due to oil leaking on spark plugs. The car had been using excessive oil. Dealer said this is known issue but I had to pay for any repairs since I was the second owner. Hyundai still pays for the original owner to get an oil consumption cleaning, but recently stopped paying for secondary owners. If the oil consumption cleaning does not work, then the next step is to replace engine, paid by customer if Hyundai refuses. Mileage on car is 75,769.

Filed Nov 22, 2025 · Engine, Fuel system · OH

I am submitting a formal complaint regarding ongoing and severe engine issues with my 2018 Hyundai Sonata SE. Despite proper maintenance, the vehicle has developed extreme oil consumption and misfire problems that have made the car unreliable, unsafe, and financially burdensome. Beginning around 118,000 miles, the vehicle started consuming oil so rapidly that I was forced to completely replace the oil every 1–2 weeks because it would run dangerously low or nearly empty. This level of oil loss is not normal, acceptable, or sustainable. I have detailed documentation, receipts, mileage logs, and maintenance history supporting this. In addition to oil consumption, the vehicle has repeatedly misfired, produced diagnostic trouble codes, and fouled spark plugs with oil. I have been forced to replace spark plugs approximately every two weeks, which is clearly abnormal for any modern vehicle. On multiple occasions, the vehicle has experienced violent knocking noises, severe loss of power, hesitation during acceleration, and near-stalling. One incident was so loud and aggressive that it felt like the engine was going to come out of the hood. These symptoms pose a serious safety risk while driving. I brought the car to a Hyundai dealership at approximately 118,000 miles for an oil-consumption test. The vehicle failed that test, clearly confirming excessive oil consumption. Despite this, Hyundai refused to provide repair, internal engine cleaning, or engine replacement, claiming the vehicle was already over 100,000 miles I have maintained this vehicle responsibly and have documentation of regular oil changes, spark-plug replacements, inspections, and diagnostic reports. Despite my efforts, the issue continues to worsen, and the vehicle remains unsafe and unreliable. This ongoing problem has caused significant financial strain, emotional stress, lost time, and fear of engine failure while driving. Based on countless similar complaints from other Hyundai owners, this appear

Filed Nov 10, 2025 · Engine · IA

My 2018 Hyundai Sonata’s oil light flashed briefly while driving, so I checked the oil level and found the dipstick completely dry. The car has been maintained regularly and was still about 1,000 miles away from its next scheduled oil change. There are no visible leaks, and the engine is not smoking. I had to immediately add oil to prevent engine damage. This appears to be a case of excessive oil consumption, which I have since learned is common in Hyundai Sonatas with this engine. I am very concerned that low oil pressure could cause engine failure or sudden loss of power while driving, creating a serious safety hazard. I request that the federal safety agency investigate this issue for 2018 Sonatas, as many owners are reporting similar experiences, and Hyundai has issued a Technical Service Bulletin (TSB 23-EM-008H) about excessive oil consumption but no recall.

Filed Aug 15, 2025 · Engine · OH

Component or system that failed or malfunctioned: The 2.4L Theta II engine in my 2018 Hyundai Sonata is consuming an excessive and unsafe amount of engine oil—approximately 1 quart every 750–1000 miles. The engine has not seized or failed yet, but the oil consumption is abnormal and dangerous. The engine is available for inspection upon request. Safety risk: This oil consumption issue poses a significant safety risk. If the engine runs out of oil unexpectedly, it could lead to catastrophic engine failure and sudden loss of power while driving—potentially causing a serious accident. The lack of warning or engine light prior to dangerously low oil levels increases the risk. Reproduction/confirmation: The issue has been reproduced and documented by a certified Hyundai dealer through an oil consumption test. However, despite confirming the problem, Hyundai has refused to cover the repair. Inspection history: The vehicle has been inspected by a Hyundai dealership. No other independent agencies (e.g., insurance or police) have inspected it. Warning lamps or messages: No warning lamps appeared before the engine oil was found to be dangerously low. There were no check engine lights or oil pressure warnings prior to discovering the oil consumption issue. Other key information: Hyundai refuses to cover the repair due to the fact that I am not the original owner—even though the original Powertrain warranty would have covered the issue if I were. Hyundai arbitrarily reduces the powertrain warranty to 5 years/60,000 miles for secondary owners, despite the safety risks being identical regardless of ownership. Furthermore, this exact engine has been the subject of multiple lawsuits and class actions due to excessive oil consumption, connecting rod bearing failure, and engine seizure. Hyundai has acknowledged the defect in various settlements but continues to deny coverage for affected owners like me.

Filed Jun 11, 2025 · Engine, Transmission · PA

The car in recent months has twice lost power and been rendered in operable on the side of the road until it could be limped home. I had the car serviced last year for a recall of a fuel filter gasket and at that time I was informed that I also had an update done for a (k knock?) sensor prior done on the car before purchase. I inquired about what that was, and they told me at the time it was for an engine recall because that particular engine I have is known to have rod bearing failure and consume oil without any trace of where it goes and piston rattle. I told the gentleman after my fuel gasket was taken care of that I would like to look into that because I have the symptoms and would like to know. At that point in time, I was told that I may have to do an oil test to see if the car loses oil. I said well can we do that and he told me it's $300 out of pocket. I asked on average before anything ever done by Hyundai, how many times do people have to do this? He said 4 to 6 in his experience. I told him I did not have the money, but I will keep an eye on the car. Everything's been fine for six months a few months ago Randomly driving to work the car shut down on me. We got the car home and my fiancé did an oil change and new spark plugs and the car worked fine. June 9th 2025 on my way to work the issue happened again in the middle of traffic. I called my fiancé and we got the car home. He performed another oil change and spark plug replacement and took pictures this time because the spark plugs are gunked up. The car now runs again. He called Hyundai of America on my behalf to just ask them if they could set up the test to see if the car was failing and they told him that they were all independent Hyundai and he would have to pay the test fees. He told them in a formal email that he doesn't believe under the federal recall He is responsible for that and they answered back that he may be reimbursed. We are contacting you because we were advised to on the issue

Filed Apr 22, 2025 · Engine, Steering · MD

The engine stalls when driving, loses power, hard time to start. It uses an extensive amount of oil. Losing power/stalling can result in accident or fire in my engine. Yes check engine light came on said it was coils/plugs changed them 2xs already. Took it to a mechanic was told there’s a recall on engine it’s a valve that is not getting air through that can potentially case a Fire in my engine.