general problems of the 2018 Hyundai Sonata - part 2

Oil consumption was ridiculously high, changing oil/topping off oil constantly. Car would not accelerate over 30 mph without sputtering and rumbling. I had mechanic diagnose bad sparks plugs due to sitting in oil from leaking. After I had them repaired/replaced the car drove great for 1 day, then decided to die in the middle of a busy intersection while I had my teenage son in the car with me. My son and I had to push it out of the busy intersection onto a side street to get out of the way! I had it towed to Hyundai dealer who said the spark plugs were bad and that the fuel pressure sensor and gdi pump were faulty and needed replacement. Left front lower control arm/ball joint assembly also requires fix. To the tune of $3000 + . It’s been at dealer for past few months until I can afford the repairs including the 2nd diagnostic and tow it took to get it to dealership.

Multiple critical mechanical and safety issues have occurred with my 2018 Hyundai Sonata sport. The vehicle has experienced persistent engine misfire, a severe oil leak, emissions system failure, and extensive paint deterioration. A certified technician confirmed an active oil pan leak with no dashboard warning lights, posing a fire and stalling hazard. To prevent further damage, I replaced the entire oil pan and spark plugs at a personal cost of approximately $800 at firestone complete auto care. The check engine light revealed diagnostic code p0420 – catalyst system efficiency below threshold (bank 1). An o’reilly emissions scan confirmed the catalytic converter failure, and emissions status was marked “red. ” the vehicle will not pass an obd-based emissions test. At 149,219 miles, Hyundai refused warranty coverage due to mileage. A certified Hyundai dealership quoted $3,722 to replace both the catalytic converter and valve cover gasket, which remains unaffordable and unrepaired. In addition, the factory-applied white paint began peeling severely from the hood and roof. Although Hyundai issued a warranty extension for this known defect, the dealership refused to repaint the hood, citing a minor dent — even though the peeling is clearly unrelated. The exposed metal has started to rust, risking structural deterioration. All concerns have been evaluated by certified Hyundai service and independent professionals. These combined mechanical, emissions, and exterior failures raise serious safety and durability concerns. I am filing this report to document manufacturer-related defects that may affect other owners of this model and year.

Summary of the problem: my 2018 Hyundai Sonata has a serious engine defect related to excessive oil consumption. Despite proper maintenance, the vehicle consumes large amounts of oil between service intervals. This has caused the engine to seize and the car’s software to restrict speed to 40 mph while driving, creating a dangerous situation on public roads. Details: vehicle purchased from an authorized Hyundai dealer in massachusetts (second owner). Issue first identified around 65,000 miles. Inspected multiple times at stevens creek Hyundai (san jose, CA). Service center confirmed this is a known internal engine issue but refused to replace or repair unless the engine completely fails. I was told to “keep topping up oil,” which is not a safe or permanent solution. Safety concern: sudden engine seizure or restricted speed while driving could result in an accident, especially on highways. This defect places me and my family at serious risk of injury or death. Requested action: I urge NHTSA to investigate Hyundai’s handling of this engine defect and require Hyundai to repair or replace affected engines before they fail, regardless of ownership status. Consumers should not have to wait for catastrophic engine failure to receive assistance.

I have a 2018 Sonata. It has thrown a p1326 code. There is a TSB for that code where the dealership will check to see if the engine will be replaced. My car passed that test meaning no engine replacement. My car has 107,000 miles on it and has had regular maintenance. In between oil changes I’m having to add oil. I’m spent hundreds on engine oil since taking owenship of the car. There is obviously an issue with the engine since there is a TSB. Yes my car passed”passed the test this time” (I’m having to pay $600 to replace the knock sensor). I feel like I’m driving a ticking time bomb and money pit. I feel as though Hyundai should handle this known issue. I need help.

My car is consuming oil. Hyundai knows this is happening with the theta ii engines. I was told to bring it in and do an oil consumption test which shows my car is consuming 1 qt oil every 406 miles but was denied help due to it being high mileage and not under warranty. My car has now started misfiring due to cylinder 1 & 2 consuming oil.

Burning a lot of oil had car 11 months only drove a few month,now it’s a tapping sound dealer where I purchase will not help nor will Hyundai dealer 15,000$ out the window now I need to get the lifters fix I can’t take it. I feel like I’ve been had. Now I got to figure to fix the car out of pocket however o haven’t had the car 1 year yet 81,000 miles.

I have to put a quart of oil in every week. It burns oil.

Burns oil fast. 900 miles from an oil change the car oil stick was empty. There are no signs of oil leaking. Every 1000 miles you have to place oil back into it. I’m not the only one complains of this issue. I was reading on reddit and it’s thousands of people having the same issue.

The contact owns a 2018 Hyundai Sonata. The contact stated that the vehicle needed multiple attempts in order to start. The contact stated that once the vehicle was started, she noticed that the low engine oil pressure light was illuminated. The vehicle was taken to a local dealer, where it was determined that an oil consumption test needed to be completed. The vehicle was not repaired. The contact had stated that prior to the oil test being recommended, she had observed that the vehicle was consuming approximately five quarts of oil per 2,000 miles. The manufacturer was notified of the failure. The failure mileage was approximately 57,000.

My 2018 Hyundai Sonata (approx. 60,000 miles) began consuming excessive oil, and the engine started smoking while driving. My wife barely made it to the dealership — the car was unsafe, struggled to stay running, and visibly smoked from under the hood. Hyundai acknowledged the oil issue but refused to cover engine replacement. Instead, they approved a one-time combustion chamber cleaning and requested we drive the car 1,000 miles to "see if it gets better. " this is a major safety concern. The vehicle is part of a group of Hyundai models known to have defective theta ii engines that have led to engine failure, fire risk, and recalls. This issue is widespread, and Hyundai is not taking proper responsibility for defective engines in cars like mine.

The engine burns oil, I have to get spark plugs every two months, and put oil in it almost every week. The check engine light is now flashing and is throwing more sensors. The paint on this car is also all peeling off.

I was going 80 mph on the interstate and suddenly my car went into limp mode and shooked really hard and dropped to 60 mph. I had to swerve to go onto the side of the road. The car behind me almost rammed into me. I contacted hampton Hyundai for days to schedule an appt. I finally was able to drop off my vehicle to them but now they are telling me they have to do an oil consumption test but my car is in limp mode and it shakes when I drive it. The car is dangerous and they are trying to charge me $500 for a fuel pump replacement ( which I have a warranty of but they notified me that does not count but it matches exactly the possible reason). As you can see in the documents, they did not note that my fuel pump was broken. They just asked if I wanted to pay it so they can get started. I get normal oil changes done. They haven't even done a rod bearing test but just looked at the knock sensor and was telling me that they wanted to charge me to get that changed.

In December 2024, my 2018 Hyundai Sonata went into limp mode after the knock sensor was triggered. This happened when my son was driving home from school. I took it to my local mechanic and he said the car was low on oil. We put more oil in it and reset the sensor. In March, the knock sensor was triggered and it again went into limp mode while my son was driving back to school. We took it into a shop and it was again low on oil. Oil was added and then the sensor was reset. The sensor went off again later in March and our mechanic told us to take it to Hyundai and have it checked for the rod bearing issue common with this model and year of Hyundai. He cleared the error and when I contacted the dealer, they said they needed the warning lights on to do a diagnosis. The car was driven for 4 months and the knock sensor went off again. I took it to the dealer and they checked the bearing clearance and it passed the test. The oil was also low and the dealer recommended doing a combustion chamber clean. I spent $564 to get the combustion chamber cleaned. Less than three weeks later, the knock sensor went off again. I took it to the dealer and they measured the bearing clearances and they came back as "passed". I elevated the complaint to Hyundai and they responded that they will defer to the dealer technicians' recommendations and findings and did not offer to do anything to help. The dealer the drove the car to see if they could trigger the knock sensor which was unsuccessful. After expressing my disappointment and dissatisfaction, the dealer said there was nothing else they could do and the car was returned to me. I am concerned with the safety of this vehicle as entering limp mode on a highway represents a safety issue that Hyundai does not seem to be concerned about.

The engine is burning through oil at a rapid rate. I probably get 2,000 - 2,500 miles before it needs a complete refill and the problem is getting worse. I was not due for an oil change recently around 2,500 miles and my engine started shaking, took it to the shop and the oil was gone without the oil light going off. This resulted in me needing to replace spark plugs and all engine coils. The repair shop recommended I sell my car because of the amount of Hyundai's he sees with this issue.

This engine consumes oil rapidly to the point I have to add quarts of it constantly . This results in the spark plugs deteriorating at a rapid rate and the coil packs as well. The car only has 75,000 miles but the problems began to start around 69,000 miles because of these issues and the engine and burning oil because of the rings and pressure it begins to shake rapidly and sputter and stall out.

Possible engine recall engine makes nose continuously stay low on oil. Bulletin came out about possible engine recall.

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.

The engine shuts off, doesn’t start, check engine light flashing, losses power, jerks while driving it, I will get it up yo speed then will shut off or won’t move.

The contact owns a 2018 Hyundai Sonata. The contact stated that the oil pressure was prematurely lower. The contact stated that while performing the oil change as an independent mechanic, the contact noticed that there was a significant amount of oil in the oil catcher, and the oil pan was fractured. The vehicle was taken to the dealer, where the contact was informed that the oil pan replacement was not covered under warranty. The vehicle was not repaired. The contact related the failure to NHTSA action number: dp22003 (engine). The manufacturer was notified of the failure and a case was filed. The failure mileage was approximately 64,400.

- component or system that failed: engine (cylinder #4 misfire) - safety was put at risk twice: once when knock sensor went off on interstate (October) and engine went into limp mode (aka protection mode). Required a tow from the, which was tricky with a vehicle full of passengers. Safety was put at risk gain when vehicle began to stutter/sputter on interstate (December). Drove 4-cylinder vehicle essentially on three cylinders an hour to dealership - problem has been confirmed by dealer (southern states Hyundai, raleigh, nc) - vehicle has been inspected by warranty inspector, who requests approval before disassembling engine to diagnose issue. However, based upon maintenance records and manufacturer's history of engine issues (more on this below), owner should not be liable for investigating a well known issue. At the time of this writing, the issue has been escalated beyond the dealership and warranty to Hyundai motor America, and currently awaiting the results of their findings. - symptoms of the problem include constant oil leak from vehicle purchase in may 2024 up to engine failure in December 2024. Various temporary remedies (oil changes and repairs, including oil drain plug gasket replacement, crush washer replacement, and replacement of cracked oil pan) did not fix the issue. Additionally, in the October incident, Hyundai dealership (sport durst Hyundai, durham, nc) simply updated the knock sensor detection (kds) software, despite the vehicle previously receiving the update in 2019 (this can be verified). Finally, owner, noted "engine knocking" (aka 'tapping') in vehicle prior to engine failure. - Hyundai (the manufacturer) settled a class action lawsuit in 2021. Vehicle is one of the vehicles listed under class vehicles, but dealer, nor warranty company, nor Hyundai seem to want to resolve issue, which both alienates owner and presents a safety hazard, as the vehicle is unsafe to drive. All claims here will be supposed via documentation and images.

The contact owns a 2018 Hyundai Sonata. The contact stated that while receiving an oil change, the technician advised that the oil level was very low. The contact stated that the low oil warning was intermittently illuminated. The contact was advised to take the vehicle to a dealer to be diagnosed. The contact had taken the vehicle to a local dealer, where an oil consumption test was performed. The contact was advised that the vehicle was operating normally. The contact stated that the low oil warning light was illuminated again. The vehicle was taken back to the same dealer, and the oil level was topped off; another oil consumption test was suggested. The contact researched online and related the failure to a known issue of oil consumption that could lead to engine failure. The contact called the manufacturer and asked about an engine replacement because the vehicle was still under warranty. The manufacturer informed the contact that a combustion cleaning had to be performed to determine if the engine needed to be replaced. The contact stated that the vehicle was taken back to the same dealer who performed the combustion cleaning; however, the excessive oil consumption remained, and there was evidence of burned oil coming from the exhaust pipe. The contact called the dealer and was advised that another oil consumption test and combustion cleaning were needed. The vehicle was not repaired. The failure mileage was 103,235.

The contact owns a 2018 Hyundai Sonata. The contact stated while driving at an undisclosed speed, the check engine warning light illuminated. The vehicle was taken to the dealer where it was diagnosed that the engine had failed and needed to be replaced. The manufacturer was contacted and approved the engine replacement. The vehicle was repaired; however, the contact stated that the check engine warning light continued to flicker on the instrument panel. The dealer was not contacted. The vehicle was not diagnosed or repaired. The manufacturer was not made aware of the most recent failure the approximate failure mileage was 111,000.

The contact owns a 2018 Hyundai Sonata. The contact stated while driving at an undisclosed speed, the vehicle lost motive power. The check engine warning light was illuminated. Additionally, engine oil was leaking onto the ground while the vehicle was parked. The contact stated that the dealer had previously replaced the spark plugs, and cylinders #3 and #4 twice, and an independent mechanic had replaced the front driver's side cv axle. The vehicle was towed back to the dealer, who determined that the engine had internal defects. The contact was informed that the engine and front cv axles needed to be replaced. The vehicle was not repaired. The manufacturer was made aware of the failure but refused to replace the engine. The failure mileage was approximately 86,800.

See attached document for complaint.

The contact owns a 2018 Hyundai Sonata. The contact stated that while driving at 55 mph, the vehicle suddenly lost motive power and was unable to accelerate above 60 mph. The check engine warning light was illuminated. The vehicle was taken to the dealer, who diagnosed a failure with the knock sensor. The vehicle was repaired, but the failure reoccurred. The contact stated that later while driving at an undisclosed speed, the vehicle inadvertently lost all motive power. The contact was able to coast to the shoulder of the roadway, where the vehicle failed to restart. The check engine warning light was illuminated. The vehicle was towed back to the dealer, who diagnosed a failure with the connecting rod bearings. The contact was informed that metal was observed within the engine and that the engine would need to be replaced. The vehicle was not repaired. After investigating the failure, the contact related the failure to NHTSA campaign number: 21v727000 (engine), but the VIN was not included. The manufacturer was notified of the failure, a case was opened, and the contact was referred to the NHTSA hotline for assistance. The failure mileage was 67,000.

43000 miles on car. Original owner. New battery. Car does not cold start in the morning. All electronics light up, but engine doesn't start. This is a known issue from all the posts I found online, yet Hyundai has not issued a recall. I paid 300 for a battery 2 weeks ago and the issue didn't resolve. Now I am being told by dealer it is the starter and it's not covered because my 5 yr warranty is expired (my car is 6 years old). This is a known safety issue across the 2018 Sonata line. This should be a recall or bulletin, instead I have to come up with hundreds of dollars more to replace a starter on a car with only 43,000 miles.

I bought my daughter this car a little over a year ago to drive to college. A few weeks after we bought the car we noticed the engine oil was low. We began checking it and had to continuously add more oil between oil changes. Now we are having to put 1-1 1/2 quarts of oil in her car every week. It also smokes when it's first crank and when accelerating. I am worried it will break down on her while driving to or from school, or in the middle of an intersection where she could be run over or hurt. We now owe more money than it is supposed to be worth, and we are stuck. When the oil gets low there are no warning lights or anything that comes on to let us know it's low. We have to keep a constant check on it. From what I am seeing online, this is a common problem with the engines in these cars. So many people are having their engines blow, and it also causes the catalytic converters to go out on these cars. We are not the 1st owners, and it is not u der warranty, so Hyundai won't do anything to help us. Even if they did, they are charging people around $1000 to clean the engine and then making people do oil consumption tests where they over fill the oil so that it doesn't run out in the time they make you drive it. This company is not standing behind there cars and they know these engines have problems! the car is available for inspection.

The electrical and engines in these cars are horrible . The steering wheel keeps locking up while driving cause everything to flick inside the car . This is a major safety issue for me when I am driving and I am unable to control the steering wheel. Dealership claimed they don’t see the issue with the car which I am stating . The vehicle was only inspected by a mechanic and since Hyundai said they couldn’t find anything a 3rd party confirmed that this was a ongoing issue and dealership could’ve caught it but it’s cheaper the sell the car . No everything happens at once especially if I’m turning or driving under 40 mph. First appeared 15 days after I bought the vehicle I alerted the dealership immediately.

To whom it may concern, my name is [xxx] , and I am formally escalating serious ongoing issues with my 2018 Hyundai Sonata. Despite repeated attempts to resolve these concerns through the dealership, my vehicle continues to experience excessive oil consumption, engine failures, and additional mechanical issues, all while under warranty. I am now seeking immediate corporate intervention. Timeline of events and mismanagement: •2024(~62000 miles): first reported oil leak and excessive oil consumption. Directed to complete multiple 1,000-mile oil consumption tests. I complied fully. •2024: repeatedly redirected between service advisors, received conflicting instructions, misleading guidance, and poor communication. No effective resolution was provided. •2025: completed extensive additional diagnostic testing as requested. Despite full compliance, no clear corrective action was taken. •2024–present: vehicle brought to Hyundai on us 19 in new port richey approximately 13–15 times for engine-related concerns. Each visit demonstrated neglect, miscommunication, and failure to properly address documented issues. •February 11, 2026: after proper diagnostics, vehicle found to have two additional oil leaks, including a head gasket and valve cover requiring replacement, with total estimated repair costs exceeding $3,000. I was advised I must repeat all testing already completed in 2024 before final determination. •vehicle is currently at 71,332 miles. Impact: •delays and repeated unnecessary testing pushed my vehicle beyond warranty limits. •mismanagement caused significant financial burden, emotional stress, and frustration. •if initial oil consumption issues had been properly addressed under warranty, the current extensive engine failures could likely have been avoided. Immediate requests: 1full review of my complete service and diagnostic history. 2warranty or goodwill coverage for all necessary engine repairs, including head gasket and valve cover information redacted pursuant to the freedom of information act (foia), 5 u.

I have had to have the starter replaced twice, I have had to change the spark plugs 5 times. I have to put oil in it about every 3 weeks. White smoke comes out of the muffler. The mechanic said I need to have an oil consumption test, which Hyundai will not covet.

Approximately 6-8 weeks ago, I was driving home and my oil light began turning on and off. This had never happened before. It was nighttime and I was only a few miles from home so I continued driving. The next morning, I checked the oil to find that the reservoir was bone dry. There had been no warning light whatsoever prior to this incident. At this point, the vehicle had about 65,000 miles on it. I had to put 2 quarts of oil in before it would even register on the dipstick so I could get it to my mechanic. Upon arriving to his business, he explained that Hyundai is well aware of this ongoing issue of oil consumption but they are doing nothing about it. I had not driven excessive miles without an oil change and faithfully get it changed between 3,000-5,000 miles, which is perfectly acceptable for this vehicle. I have all receipts from these changes. I have begun to maintain a record indicating the oil that I have added over the last 1,700 miles. It has been 2. 5 quarts. The morning I brought the car to my mechanic I reached out to the Hyundai dealership and was told I would need to pay for a diagnostic, then two oil consumption tests. I declined and promptly reached out to Hyundai corporate. They told me the same nonsense and then offered to have their consumer division reach out to me. Ultimately, that person told me I would need to do the same thing, so they were entirely useless in facilitating any reasonable resolution. I subsequently found out about the oil consumption problem that thousands of people have reported in various models and years. I joined a few Hyundai oil consumption groups on facebook and now realize how many people have been impacted by this issue. I still owe $5,600 on the car but feel that the issue will not be handled by Hyundai and don't wish to have ongoing concerns with driving the car and constantly topping it off with oil. As a result, I feel that I am forced to pay off this car and buy something else.

2018 Hyundai Sonata with only 128k miles already needs a new engine due to oil consumption. I have done the regular maintenance on the car and have only put roughly 25k miles on the car since owning it.

Vehicle is loosing a quart of oil every two weeks. When taken in for service no problems found. Dealership says their is a known engine problem but since I am the second owner no warrenty applies. Their suggestion is to constantly pit oil in the vehicle. This problem has effected many Hyundai owners and should be on the company to fix the problem.

While driving on the freeway the car would not accelerate over 45 mph and then began to lose acceleration all together. The oil and engine lights came on and we were able to pull to the shoulder. Turned the engine off and then was unable to restart. Losing power on the freeway would be considered a safety risk. The car was towed to the mechanic who checked the oil and found it was three quarts low, however, two months prior the oil had been changed along with the oilpan being replaced as it was cracked. It was then towed to the dealership and after three months of diagnostics and inspections I was told the engine needed to be replaced. The Hyundai dealership is unwilling to share any communications between them and Hyundai USA. In 2019 the ecm was updated per recall 953. The car is available for inspection at your convenience. I think it's important to note that this is a six-year-old vehicle with under 55,000 miles.

My car is part of a campaign due to rod-bearing failure where the engine experiences problems such as complete failure, vibrating, hesitating, engine light on, and oil light on. I've been communicating with Hyundai who is not helping me with this issue. I was advised by them to continue driving the car "until the engine seizes", or I hear "a loud knocking noise". Upon inspection, three local Hyundai employees "agreed 100%" I need a new engine. However, per these employees Hyundai corporate will not approve the replacement even though the vehicle is constantly experiencing the above symptoms above, simply because there is not a "loud knocking noise" coming from the engine. Even though all the other issues are present. This is very unsafe. I have a minor child I take to school daily, for an advisor to advise to drive the vehicle until "the engine seizes" is extremely dangerous, especially when they are aware my VIN is associated with engine replacement. My car exhibits symptoms of a rod-bearing failure and this multi-billion dollar company is taking advantage of hard-working urban mothers, by turning a blind eye and trying to require me to pay thousands of dollars up front for a problem they created by selling a vehicle with faulty engine. Again, the technicians indicated I in fact do need the engine replaced, but that Hyundai corporate will require me to pay for a diagnostic test, rod-bearing test, and engine compression test because corporate does not take their word for it. The fact a auto manufacturer is advising people to drive in such an unsafe manner is disheartening. If my child and I get injured in an accident by following their advice, our blood will be on their hands!.