2018 Kia Optima Problems

What owners report

Most owners of this model year describe engine-related problems: oil that disappears between changes, warnings that go off, knocking or ticking sounds, and occasional loss of power or stalling. The reports are spread from very low mileage up to well past 100,000 miles, with a cluster of oil-consumption and limp-mode accounts in the 60,000-110,000 mile range. A smaller but noticeable group concerns the panoramic sunroof, brakes, and electrical/starting behavior.

1. 1
   Engine

   Excessive engine oil consumption and low-oil warnings

   • 89 complaints (38%)
   • median 76,270 mi at 5.4 yrs old (21 state mileage)
   • 3 mention a crash, fire or injury
   • owner-quoted repair $686 (median of 5 quotes)
   • filed 2019–2026

   Complaints describe the oil level dropping far faster than expected — some owners say the dipstick reads empty within a week or that several quarts are needed within about 1,000 miles. Many report the oil pressure or low-oil warning light coming on, sometimes followed by hesitation, a flashing oil light, or stalling. According to the complaints, dealers performed oil changes or oil consumption tests, sometimes cleaned the engine or replaced a valve cover gasket, and in several cases the problem returned or the test could not be completed. Reported from roughly 60,000 to 100,000 miles in the sample, with some accounts as low as around 10,000 miles.

   2 related service bulletins

   What to check: Check the oil level on the dipstick and ask for oil change records or any oil consumption test paperwork. A service bulletin describes a procedure for diagnosing excessive oil consumption on these engines, so ask whether it was performed.

   2 excerpts from owner complaints in NHTSA records

   “The contact owns a 2018 Kia Optima. The contact stated that the vehicle was experiencing abnormal oil consumption. The contact stated that on one occasion, 3 quarts of oil were added to the vehicle after less than 1,000 miles of driving. The vehicle was taken to the dealer who initiated an oil consumption test. …”

   NHTSA complaint #11566222, filed 2024-01, 88,000 miles

   “The contact owns a 2018 Kia Optima. The contact stated that after starting the vehicle, there was an abnormal amount of smoke coming from the exhaust pipe. The contact inspected the dipstick and discovered that the engine oil level was low. The local dealer was not contacted. The vehicle was not diagnosed or repaired. The manufacturer was not made aware of the failure. The failure mileage was approximately 60,000.”

   NHTSA complaint #11590383, filed 2024-05, 60,000 miles
2. 2
   Engine

   Limp mode, knock sensor codes and stalling

   • 60 complaints (26%)
   • median 76,735 mi at 6.0 yrs old (24 state mileage)
   • filed 2019–2026

   Owners describe the car suddenly dropping power or entering limp mode, often at highway speed, with the check engine light on and sometimes a shudder or knocking sound. Complaints mention diagnostics pointing to a knock sensor or knock sensor detection system, and in some cases to connecting rod bearing wear. Several say a software update, spark plug replacement, or wiring harness work was done but the problem came back. Mostly between about 60,000 and 140,000 miles, often while driving at speed.

   3 related service bulletins

   What to check: Ask whether the engine control software updates were applied and whether the vehicle has had a knock sensor detection system install. Have a scan tool read stored codes before purchase, and listen for a ticking or knocking sound at start-up.

   2 excerpts from owner complaints in NHTSA records

   “The contact owns a 2018 Kia Optima. The contact stated that while her fiancé was driving at a slow speed, the vehicle inadvertently shifted into LIMP mode with the check engine warning light illuminated. The vehicle was taken to an independent mechanic where it was diagnosed and DTC: P1326 (KSDS) was retrieved. The contact was informed that there was vibration caused by excessive connecting rod bearing wear. The dealer was not notified of the failure. …”

   NHTSA complaint #11478256, filed 2022-08, 99,000 miles

   “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 complaint #11605073, filed 2024-07, 132,378 miles
3. 3
   Engine

   Engine stalling or cutting out while driving

   • 50 complaints (21%)
   • median 62,500 mi at 3.3 yrs old (18 state mileage)
   • 1 mention a crash, fire or injury
   • filed 2019–2026

   Complaints describe the engine shutting off or losing power without warning, sometimes at freeway speed, sometimes when accelerating from a stop, and in some cases restarting on its own. Dealers reportedly could not duplicate the problem in several instances; in others, work on the wiring harness, spark plugs, or fuel system followed. Reported from about 12,000 miles up to 132,000 miles, across a range of driving conditions.

   Recall 18V1610001 related service bulletin

   What to check: Ask for the service history on any stalling-related visit, and have a shop check for stored codes and engine control module software status. A hybrid propulsion recall exists for some vehicles of this generation, so confirm by vehicle identification number whether it applies.

   2 excerpts from owner complaints in NHTSA records

   “On 03/29/2019 was traveling to work. On interstate 53 southbound car went to limp mode. No power. Managed to get to dealership. They tried to repair my vehicle for 1 month after they told me that engine need to be replaced they managed to change wiring harness. After 1 month it was done. I took car back. 1 or 2 weeks later car went into limp mode again with same problem. Filed a claim with Kia and bbb to resolve it. …”

   NHTSA complaint #11241806, filed 2019-08, 14,900 miles

   “2018 Kia 12,000 miles had recall 2 months ago for software update as I was driving to work one day getting on interstate in rush hour traffic my speed at time was probably 60 MPH cant push the gas car just stalls 18 wheeler behind blowing horn I pull car to side of interstate got car to closest Kia dealership I ask what was wrong and they stated they use to replace the motor but now they just put a part called a harness on it part was not in they have to keep car several days”

   NHTSA complaint #11206044, filed 2019-05, 12,145 miles
4. 4
   Engine

   Engine noise, knocking and engine replacement

   • 57 complaints (24%)
   • median 82,000 mi at 5.5 yrs old (17 state mileage)
   • 2 mention a crash, fire or injury
   • filed 2019–2026

   Complaints describe a ticking or knocking from the engine that worsens over time, in some cases followed by a seized engine and a dealer diagnosis that the engine needed replacement. A few owners report very low mileage at the first symptom, and one describes being told the engine was replaced and then having symptoms return. Spread from under 10,000 miles to over 100,000 miles; several reports in the 80,000-110,000 mile range.

   2 related service bulletins

   What to check: Listen for ticking at idle and on start-up, check oil level and color, and ask for any engine replacement or campaign history tied to the vehicle identification number.

   2 excerpts from owner complaints in NHTSA records

   “I originally leased my 2018 Optima with 98 miles on it and bought it out at the end of my lease this was my second Optima, I also had 2 hyundai sonatas. Since I'm in sales I had the added mileage on it. At 98,000 miles the engine started ticking. I originally had a 2013 hyundai sonata that when it hit 105,000 started ticking only to find that it was burning oil (1.5 quarts a week) so I was hesitant about another Kia but the dealer assured me that Kia had been aware of the problem and that they had fixed it. Guess what?! It hasn't. …”

   NHTSA complaint #11398642, filed 2021-03, 98,000 miles

   “I leased 2018 Kia Optima ex. At 6399miles and 9650miles engine light on and car vibrates a lot. First service replaced spark plug and second time they replaced engine. This car was awarded as best initial quality award which has engine issues. Kia says they will not take any responsibility if anything happens when driving car because of the issue. If it happens again they will replace engine or repair it. Kia is not confident that replaced engine will not have this issue.”

   NHTSA complaint #11330830, filed 2020-06, 9,650 miles

Buying note. Engine oil consumption and power-loss reports are the dominant theme for this model year, so check oil level and service records carefully and confirm any engine-related campaign or software work was completed for the specific vehicle. A pre-purchase inspection that reads stored codes and listens for engine noise is worth the cost here.

Summary written with AI from a sample of 60 NHTSA complaints for this model year (picked at random, with complaints that state a mileage and recent ones taken first), then checked automatically against the source records. Where a problem shows a complaint count, every complaint for this model year was matched with fixed keyword rules (written with AI and tested against the sample), and the mileage, age and repair figures are calculated from those complaints; owners' figures are as stated, not verified. Other counts refer to the sample. The excerpts come from NHTSA's public complaint records and are unverified; capitalisation is normalised, NHTSA staff notes are removed, and shortened text ends with “…”. Something wrong? Request a correction.