2018 Kia Optima: What to check before buying

Oil disappears between changes with no visible leak. This is by far the most common report. Owners add oil every week or two and say the low-oil light comes on only when the level is already very low. They also describe fouled spark plugs, misfires, rough idle and heavy shaking. Several cases go on to a failed valve, metal in the engine or complete failure, with onset from about 72,000 miles to just over 100K. Six of the 90 complaints involve fire, including flames under the hood while driving and in a parked car.

Heavy oil burning leads to stalls, limp mode, knocking and seized engines in this group. Owners add oil every week or two, and some find the crankcase empty with the oil light flashing. Dealers have diagnosed a fractured valve, failed spark plugs and seized engines, and several said the engine needed replacing. A few owners say coverage was denied because of the car's maintenance history. Stalls happen at 40 to 65 mph, and failures appear between about 60,000 and 121,000 miles.

Bulbs burn out again and again, and headlights can switch off while driving at night. Other owners say the engine stalls or shuts off, with the power steering, battery and master warning lights coming on together. The doors can lock themselves while the engine runs with the key inside, which strands drivers. Trunk latches fail, and the trunk can fly open with no warning on the dash. Two complaints involve fire: one at bulb connections and one with sparks from under the car. Many filings here actually describe oil burning.

The car jerks, shifts hard and jolts when slowing to a stop, and dealers often find no cause. Several owners lose power at speed. They describe stalls while merging onto highways and an engine that revs without moving the car. One transmission failed at 3800 miles. Many filings again describe heavy oil burning with smoke from the tailpipe. One complaint describes a CV axle snapping in a crash, and another describes an engine fire while driving. In a third, a parked car rolled down a driveway and two people were hurt.

Power steering cuts out or goes heavy, often along with a stall and a cluster of dash warning lights. Owners say this nearly caused crashes. In one report the steering locked mid-turn with the power steering light on. Reports range from about 35,000 to 63,826 miles. Dealers often cannot reproduce the fault, and one owner replaced the alternator without fixing it. Other filings describe a failed steering column coupler, a wheel stuck at startup and theft concerns.

Crashes happen without the bags deploying in most filings here. Seven of the nine complaints involve crashes, and seven people were injured. The crashes include rear-end impacts and hits on trees and poles. Several owners also say the seat belt did not lock. In one report every bag deployed except the steering wheel bag. A separate complaint about a hybrid describes the warning light coming on with oil leaking and metal shavings in the oil.

Headlights shut off by themselves while driving at night with the switch on Auto, sometimes along with the dash lights. Owners get them back by toggling the switch, and some leave it on manual. Others say the headlights go off whenever the turn signal is used, or come on by themselves in a locked, parked car. Owners describe this as dangerous on unlit roads and freeway merges. One SX owner reports the auto-leveling LED headlamps aim lower when passengers get in.

The brake pedal goes soft and sinks to the floor. In one crash report, this sent the car into a building wall. Other owners describe a firm pedal that barely slows the car and then locks the wheels, a catching feeling near 13 mph, and brakes that are slow to release in reverse. New master cylinders, brake boosters, calipers and pads do not always fix it, and dealers often find nothing wrong. One owner reports front calipers seizing and smoking.

The panoramic sunroof shatters on its own at highway speed, with a gunshot-like bang and no impact, in two reports. Paint bubbles and peels on the driver-side door and below the rear window, including on snow white pearl cars. Other filings here describe a tire blowout under 16,000 miles followed by brake warning lights and grinding, and an engine with oil burning, oil leaks, loss of power and code P1326.