What 228 owners told NHTSA about the 2018 Kia Optima

The 2.4L Theta II engine in my 2018 Kia Optima is failing, exhibiting excessive oil consumption, with oil loss documented at over 1 quart per 1,000 miles, leading to secondary failures in the catalytic converter, clogged with oil carbon and breaking into pieces that may damage the cylinder walls, and the spark plugs, which are fouled with carbon, causing misfires. The engine and related components remain intact and un-repaired, pending Kia’s required 3,000-mile consumption test. Safety of drivers have been put at significant risk. The excessive oil consumption and potential engine seizure threaten sudden loss of power, especially on freeways where car fails to accelerate to city and highway speeds, increasing the chance of a collision. The clogged catalytic converter poses a fire hazard, (reported by NHTSA investigations into Theta II) where oil leaks or debris can ignite on hot surfaces. Risk is heightened during the mandated 3,000-mile test as well. Problem has been confirmed by both a dealer and an independent service center as recent at 1 July, '25, documenting oil loss and new engine recommendation. Symptoms began with noticeable oil loss during oil changes, starting at least 1 quart per interval on May 10, 2023 (mileage 43,374), with the loss increasing over time. Misfires and RPM loss during acceleration first appeared after the oil valve gasket replacement in late May 2025, and freeway pickup issues became apparent around mid-June 2025. The full engine failure was confirmed by Spitzer on July 01, 2025.

NHTSA ODI 11671015

Got an oil change, and they advised that it was low on oil. (I had just replaced it recently) I took it to the dealer and they advised a part was bad, that they replaced. I was driving and the check engine light and oil light came on . I had to tow car. Dealer said the engine was burning oil, and that the engine is covered, but I would have to drive it until it got worse.

NHTSA ODI 11667034

Subject: Urgent Request for Engine Replacement – 2018 Kia Optima Dear Kia Consumer Affairs, I am writing to formally report a recurring and increasingly dangerous engine issue with my 2018 Kia Optima, and to request immediate assistance, including consideration for an engine replacement due to ongoing safety and reliability concerns. Since June 2024, I have routinely visited the Kia dealership on a near-monthly basis for service due to persistent problems with excessive oil consumption and spark plug failures. Each visit has resulted in service-related expenses, despite my efforts to maintain the vehicle in accordance with manufacturer recommendations. Unfortunately, the issue has not been resolved and continues to worsen. Most recently, on [XXX], I experienced a critical incident. While driving, the engine began shaking aggressively, the check engine light illuminated, and smoke was detected coming from the engine compartment. Out of concern for my safety, I immediately pulled over and had the vehicle dropped off at a nearby garage for emergency inspection. This incident, combined with the repeated monthly service visits and associated costs, clearly indicates a systemic issue that may be linked to known engine defects in similar Kia models. I urge Kia to review my case for warranty coverage, recall eligibility, or goodwill engine replacement assistance. I have attached supporting documentation including service records, receipts, and oil consumption logs. Please advise on the next steps for resolving this matter. Thank you for your attention. I look forward to your prompt response. Sincerely, [XXX] [XXX] [XXX] INFORMATION REDACTED PURSUANT TO THE FREEDOM OF INFORMATION ACT (FOIA), 5 U.S.C. 552(B)(6)

NHTSA ODI 11666542

There is already the theta 2 campaign on my Kia optima but Kia is not upholding their warranty for a new engine. Kia customer care told me that untill my car actually throws a rod then they will not fix it. So I could be doing 80 down the freeway and jeopardize not only my safety but everyone else's for them to uphold their lifetime warranty? Also upon doing further investigation and I don't know how many cars this pertains to but the fuse box in my 2018 actually belongs to a 2016 which if you look it up yes they are comparable but don't offer all the same functions or power that my 2018 needs to run I fully believe Kia knew this when they were being built on the factory line because it just so happens that there is about 6 different versions to the pcb relay that can fit from a 2016 to a 2020 k5 but for some odd reason every car got something different why?

NHTSA ODI 11664974

The contact owns a 2018 Kia Optima. The contact stated while driving 70 MPH, the vehicle failed to accelerate as intended while depressing the accelerator pedal. The contact turned off the cruise control; however, the failure persisted, and the vehicle stalled. The contact stated that the check oil warning light was illuminated. The contact was able to coast to the side of the road. The vehicle failed to restart, and the vehicle was towed to a service station. The vehicle was then towed to a dealer where it was diagnosed and determined that the high-pressure fuel pump had failed, causing fuel intrusion into the engine and engine failure. The vehicle was not repaired due to the cost. The manufacturer was not made aware of the failure. The failure mileage was approximately 146,000.

NHTSA ODI 11662780

This vehicle has an active recall: SC218 / DTC P1326 – ECU UPDATE / ENGINE REPAIR. I brought it to Martin Kia in Newark, Delaware, but they refused to perform the recall stating that since the vehicle is owned by a used car dealer, the recall is not applicable. They also provided a written statement saying that the extended warranty does not apply because I am a dealer, and that they will not perform any recall work until the vehicle is owned by a “customer.” However, federal law requires all safety recalls to be completed free of charge, regardless of the vehicle’s current ownership status or whether it is owned by a dealership. This is a safety issue and refusal to perform recall work puts future drivers at risk. I have attached the letter they gave me for your reference. I kindly request your urgent review of this case and enforcement action to ensure the dealership complies with federal recall obligations.

NHTSA ODI 11660972

I am the current legal owner of a 2018 Kia Optima Hybrid (VIN: [XXX] ), which has an open safety recall under campaign number SC218Y3 (DTC P1326 – Knock Sensor Detection System / ECU Update / Possible Engine Repair). I attempted to schedule the recall repair with Martin Kia in Newark, Delaware. However, the service department refused to perform the recall service on the basis that I purchased the vehicle from an auction and do not have prior service records. This denial is a clear violation of federal recall regulations. As stated by NHTSA, all safety recall repairs must be completed free of charge regardless of ownership history or how the vehicle was purchased. I am now left with a potentially dangerous vehicle that Kia refuses to service, despite an active recall on file. This situation is unacceptable and puts me, as well as other road users, at risk. I respectfully request that NHTSA investigate Kia’s non-compliance and ensure they are held accountable for refusing to fulfill their legal obligations regarding this recall. I am willing to provide proof of ownership and any supporting documentation. Thank you Best regards My Contact Info: [XXX] [XXX] [XXX] INFORMATION REDACTED PURSUANT TO THE FREEDOM OF INFORMATION ACT (FOIA), 5 U.S.C. 552(B)(6)

NHTSA ODI 11660558

Burning oil prematurely causing engine to go and need replacement.

NHTSA ODI 11660200

Vehicle engine shut down without warning while driving on the interstate on April 27,2025. I had the vehicle towed and come to find out a "campaign" was issued for the vehicles engine in July of 2018. I purchased the car used in March of 2021 and was not aware of the "campaign" in which the vehicles engine was defective and could possibly cause a fire. I have reached out to KIA to see if they could help me in resolving the issue with the engine, but have yet to hear back from them.

NHTSA ODI 11659714

Mi Kia Optima 2018 con motor 2.4L GDI presenta consumo excesivo de aceite, un problema que he visto reportado por muchos otros propietarios del mismo modelo. En solo 700 millas recorridas, el aceite baja hasta el punto “Low” sin fugas visibles. Este consumo anormal puede causar fallos en el motor si no se revisa constantemente. El concesionario Kia ya revisó el vehículo, pero como no hay recall abierto, no ofrecieron solución, a pesar de que este motor ha sido identificado en boletines técnicos por este problema. Solicito que este caso sea considerado por la NHTSA para que se investigue si debe emitirse un recall extendido para los Kia Optima con motor 2.4L GDI.

NHTSA ODI 11654394

Oil consumption and engine code P200A

NHTSA ODI 11653766

Kia is aware of the engine oil consumption causing misfires, failed emissions test, blowing a rod and engine lock up. THEIR SOLUTION WAS A CLASS ACTION LAWSUIT THAT STATE ONCE THE CAR IS LOCKED UP OR ROD HAS BLOWN THROUGH THE ENGINE THEN THEY WILL FIX IT. I have had to replace the spark plugs multiple times in last 12 months due to misfires while driving. I HAVE BEEN TOLD BY THE DEALER THAT THEY CANT DOING ANYTHING TO HELP EVEN THOUGH THEY ARE AWARE THEY SUGGEST THAT I DRIVE WITH NO OIL AND LOCK THE ENGINE UP EVEN THOUGH IT COULD CAUSE A CRASH. MY LIFE SHOULD NOT BE PUT IN DANAGER FIRST IN ORDER FOR THEM.TO FIX THE ENGINE.

NHTSA ODI 11652695

The contact owns a 2018 Kia Optima. The contact stated that while driving at various speeds, the contact noticed an abnormal oil consumption. The check engine warning light was intermittently illuminated. The vehicle was taken to a local dealer, where it was diagnosed with a spark plug misfire. The vehicle was repaired; however, the failure persisted. The vehicle was towed to a local independent service center, and the spark plugs were replaced. The contact stated that the vehicle was taken to a local independent mechanic where it was repaired several times; however, the failure reoccurred. The vehicle was taken to a second local independent mechanic, where the spark plugs and other unknown repairs were made. The manufacturer was made aware of the failure. The failure mileage was approximately 100,000.

NHTSA ODI 11651118

Complaint-Car misfired, oil leaking on spark plugs causing an Engin Replacement that was first complained to Gossett Kia Covington Pike,1900 Covington Pike, Memphis, Tn 38128 on [XXX].On [XXX] complaint car shakes, misfire. Complaint to Gossett Kia South 2680 Mt.Moriah Rd, Memphis, Tn 35115. This date car stayed at dealership 3 days invoice a diagnostic was performed total amt $913.38. On 12/26/24 Mr.Macias on Mt.Moriah asked me to bring my vehicle in for another diagnostic test, amt to be charged $251.00 this time a tune up, replaced #4 spark plug that had misfired, fuel injectors cleaned I asked Mr.Macias "why would I have that done when it had been done the month before, the Tech recommended Engine Replacement. I also asked the above, what about the Tech's findings, Mr.Macias stated he would get back with me. On 1/16/25 Mr.Macias called to discuss Engine replacement (Projected Amt:$6,300). I have contacted Kia Consumer Assistance on 1/10/25 to discuss all of the above to no avail. I have been without a vehicle since 12/3/26 I am continually getting the run around, I have all invoices to verify my dilemma with a vehicle that is sitting unused. I am a [XXX] who is still making a $484.00 car payment per month. I've done my research on the 2018 Kia Optima's, only to find that the same problem that I'm having with the oil leaking on the spark plugs, misfiring , shaking, causing stalling in the middle of traffic, if this is not a hazard, what is ? This a problem that should have been corrected long ago. I would appreciate it if you would please help me. I'm tired of having to pay to get to and from Dr's. Office visits, drug stores and grocery stores. Thanking you in advance, [XXX] [XXX] or email address : [XXX] INFORMATION REDACTED PURSUANT TO THE FREEDOM OF INFORMATION ACT (FOIA), 5 U.S.C. 552(B)(6)

NHTSA ODI 11644939

My engine burns oil very bad. Black smoke comes out of my tailpipe and I burn through 5 quarts in less than a thousand miles. I just got my oil changed two weeks again and I just had to add more oil to my car bc it was empty. I’ve had to replace the spark plugs twice due to soot build up. I can’t afford a new car I’m 17 and can barely afford the maintenance let alone a whole new engine. Have spoken to many mechanics and they all say the same thing “it’s a Kia it’s gonna burn oil” ITS A KNOWN ISSUE. And yet Kia will not resolve it bc they don’t want to spend their own money to fix their mistake. I got an estimate for a new engine which is basically crucial and it’s over three grand. No matter where I take it everyone always says the same thing- to get rid of it before it’s too late. But I simply cannot afford to do that and I know my car is not the only one with this issue so many other people with the same car/engine have the same issue. 2.4 L GDI !!!!! I wish someone would have warned me before buying Kia. A recall to fix this issue is needed now. I lose control of the speed sometimes. I will keep my foot at a set position on the throttle and the engine will take off because it’s jumping to the usual power it should have. ( it has reduced power most of the time bc of the struggling engine) sometimes on the highway I’ll get a sudden burst of power and I have to let off the accelerator. Not safe at all

NHTSA ODI 11637108

Increased oil consumption with needing oil added and or changed half way before date or milage stated, oil changes performed by Kia dealer. Car staling and engine knocking while driving. Burnt smell while driving.

NHTSA ODI 11632125

I drove the car to the park about 6 miles round trip with family. I came back home and started having lunch for about 25 minutes. I then attempt to start the engine to go to my appointment but then car didn't turn on. On third attempt I had a weird noise coming out of the hood and I went back inside the house to get my gloves. When i came outside of the house, the hood of the car was in flames. I called 911 to turn off the fire. The car is now at a total loss.

NHTSA ODI 11628268

The contact owns a 2018 Kia Optima. The contact stated that while his wife was driving at an undisclosed speed, the vehicle went into LIMP Mode, and the check engine warning light was illuminated. The vehicle was restarted; however, the failure recurred while driving. The vehicle was taken to the dealer, where it was diagnosed and determined that the spark plugs had failed and needed to be replaced. The vehicle was repaired; however, the failure recurred while driving. The vehicle was towed to the dealer, where it was diagnosed that the engine had failed and needed to be replaced. The contact was informed by the dealer that the repair could not be covered due to the poor maintenance of the vehicle; however, upon providing all the maintenance records, the dealer informed the contact that the vehicle could not be repaired unless the engine had fully seized. The dealer offered a trade-in offer; however, the contact declined the offer. The vehicle was not repaired. The manufacturer was made aware of the failure. The approximate failure mileage was 111,000.

NHTSA ODI 11627569

Check engine light began flashing halfway down the highway. Oil changes and maintenance are done regularly. Vehicle handling seemed to be unsafe. Vehicle would not accelerate. Had inspection done in September.

NHTSA ODI 11627235

Engine is burning oil at a high rate have to add at least three quarts twice a week and headlights and brake lights got out twice a month

NHTSA ODI 11619614

The contact owns a 2018 Kia Optima. The contact stated while driving approximately 40 MPH, the accelerator pedal was depressed; however, the vehicle failed to respond as needed. The contact stated that there was an abnormal growling sound coming from under the floorboard, and the engine was making an abnormal knocking sound. The contact stated that the RPM gauge was revving high while depressing the accelerator pedal; however, the vehicle failed to respond. The contact pulled over and turned off and restarted the vehicle; however, the vehicle was not running normally. The contact stated that the failure was a recurring failure. Additionally, the contact stated that vehicle was consuming approximately one quart of engine oil per week and the transmission was hesitating and was making the vehicle jerk while shifting gear. The contact had taken the vehicle to an independent dealer, but the vehicle was not diagnosed or repaired. The manufacturer was informed of the failure. The failure mileage was 76,270.

NHTSA ODI 11617527

I’ve had the 2018 Kia Optima for a little over a year. I purchased it as a used vehicle. I’ve noticed that the car is utilizing an excessive amount of oil. Each time I get an oil change for the vehicle I am having to purchase oil to refill the vehicle about 2weeks to a month after. I’ve made multiple road trips where I’ve gotten the oil changed before leaving and I drove around 350 miles; halfway through the drive the oil was half empty on the dipstick. The first time this happened I was unaware of this issue and when I arrived to my destination after around 350 miles of driving, the car had little to no oil. I will provide store receipts of each time I had to purchase oil for the vehicle. I will also provide service interval receipts upon request. Dates of oil purchase are as follows: 1.7/18/23 2.8/16/23 3.10/20/23 4.12/18/23 5.2/7/24 6.2/29/24 7.3/18/24 8.5/4/24 9.5/11/24 10.7/9/24 Service intervals for oil changes are kept up with every 3-5k miles and can provide maintenance receipt.

NHTSA ODI 11614674

Car cut out and stutters and the engine light flashes. Code P1326 is displayed on the OBD reader.

NHTSA ODI 11611014

The contact owns a 2018 Kia Optima. The contact stated while driving 20 MPH, the vehicle hesitated upon depression of the accelerator pedal with the check engine warning light illuminated. The contact continued to drive the vehicle however, the vehicle failed to accelerate above 40 MPH and was shaking abnormally. The vehicle was not diagnosed or repaired. Neither the dealer nor the manufacturer was notified of the failure. The failure mileage was 132,378.

NHTSA ODI 11605073

Have completed 4 oil consumption tests and replaced knock sensor and now have knocking in the engine

NHTSA ODI 11602764