2020 LEXUS RC 300

Typical onset: 40,000-70,000 mi

Symptoms: rough idle when cold, hesitation on acceleration, reduced fuel economy, occasional misfire codes P0300-P0304

Fix: Direct-injection engines have no fuel wash over valves. Walnut blasting the intake manifold runners takes 3-4 hours, requires intake removal. Some shops use chemical induction cleaning as a temporary Band-Aid, but walnut media is the real fix.

Estimated cost: $450-750

Typical onset: 60,000-100,000 mi

Symptoms: metallic knock at idle that worsens with RPM, low oil pressure warning, metal shavings in oil filter, sudden catastrophic engine failure if ignored

Fix: The 8AR-FTS has thin bearing tolerances and some batches see premature wear, especially if oil changes were stretched. Bearing replacement alone is 12-15 hours with crank polishing if journals are scored. If a bearing spun and damaged the crank or block, you're looking at short-block replacement or full rebuild at 25-35 hours.

Estimated cost: $3,500-8,500

Typical onset: 50,000-90,000 mi

Symptoms: red ATF puddle under engine bay, transmission temperature warning light, burnt ATF smell, slipping or delayed shifts if fluid level drops

Fix: The crimped fittings on the cooler lines to the 8-speed can weep or crack. Line replacement is 2-3 hours, includes ATF drain/refill and sometimes requires radiator removal for access. Cooler itself rarely fails, it's the hard lines.

Estimated cost: $600-1,100

Typical onset: 60,000-100,000 mi

Symptoms: clunk on shifts from P to D or R to D, vibration at idle in Drive, drivetrain jolt on hard throttle

Fix: The rear trans mount wears and sags. Replacement is straightforward, 1.5-2 hours with a trans jack. OEM mount costs more but lasts; aftermarket polyurethane mounts are stiffer and transmit more NVH.

Estimated cost: $350-550

Typical onset: 70,000-110,000 mi

Symptoms: rough running after long highway drives, intermittent misfire on one cylinder, fuel trim codes P0171/P0174

Fix: Direct injectors run hot and can coke up. Removal and ultrasonic cleaning is 2-3 hours for all four. If injectors are electrically failing (not just fouled), replacement is $200-300 each plus labor.

Estimated cost: $500-1,200

Typical onset: 80,000-120,000 mi

Symptoms: rattle from engine bay on cold start that fades when warm, occasional overboost or underboost codes P0234/P0299, loss of power under boost

Fix: Wastegate actuator arm wears or the flapper gets carbon-locked. Turbo R&R is 6-8 hours due to tight packaging. Actuator replacement or turbo rebuild if shaft play is present. Full turbo swap if housing is cracked.

Estimated cost: $1,800-3,200