One problem related to crankcase (pcv) has been reported for the 2018 Hyundai Sonata. The most recently reported issues are listed below. Please also check out the statistics and reliability analysis of the 2018 Hyundai Sonata based on all problems reported for the 2018 Sonata.
Excessive oil burning and oil consumption. Oil turns black abnormally quickly (within the first 500-1000 miles) even though recommended full-synthetic oil is used. Engine has intermittent rough idle once engine is warm. Occasionally engine experiences "near-stall" and "misfire event", causing the battery light to flash on dashboard. >>>oil consumption rate is approximately 3-4 quarts per 1,000 miles<<< ***maintenance completed since purchase*** coolant flush - replaced pcv valve (new) - replaced valve cover gasket + oil pan / oil pan gasket (recommended by dealer) (new) - replaced spark plugs (recommended by dealer) (new) - replaced battery (new) - replaced alternator (new) - replaced both engine accessory belts (new) - replaced 150a main fuse (located on positive battery terminal) (new) - used Hyundai brand oil filters - used chevron/techron complete fuel system cleaner twice, between and at oil change (as recommended by "twin city Hyundai" dealer in alcoa, TN) ** dealership inspect it for approval of known federal recall on gdi engines for excessive oil consumption / engine seizing issues; dealership claimed it did not pass re-call approval*** symptoms still persist mileage is now approx. 80k.