The 2018 Q70L is the long-wheelbase version of Infiniti's aging Y51 platform (2011-2019), sharing DNA with the 370Z and previous-gen M-series. The 3.7L VQ37VHR V6 is generally reliable, but the 5.6L VK56VD V8 has catastrophic oiling issues that can destroy the engine, plus both share transmission cooler and driveline problems typical of this platform's final years.
5.6L V8 Oil Gallery Gasket Failure Leading to Engine Destruction
Common · high severityTypical onset: 60,000-120,000 mi
Symptoms: Low oil pressure warning at idle when hot, Ticking/knocking from valvetrain that worsens with heat, Eventual catastrophic bearing failure and spun rod bearings, Metal shavings in oil filter during changes
Fix: The VK56 has internal oil gallery gaskets that fail, starving bearings. Preventive fix requires engine-out teardown to replace all gallery gaskets, bearings, and timing components (25-35 hours). Most owners only discover it after bearing damage, requiring short-block or complete rebuild (40-60 hours). Some shops won't touch it and recommend reman/used engine swap instead.
Estimated cost: $8,000-15,000
Transmission Oil Cooler Internal Failure (Coolant-Trans Fluid Cross-Contamination)
Common · high severityTypical onset: 70,000-110,000 mi
Symptoms: Strawberry milkshake appearance in coolant reservoir or transmission fluid, Transmission slipping, delayed engagement, or shuddering, White smoke from exhaust if coolant enters trans, Engine overheating if trans fluid enters cooling system
Fix: The external trans cooler in the radiator fails internally, mixing ATF and coolant. Requires radiator replacement, complete transmission flush (sometimes multiple flushes), and often transmission overhaul if coolant circulated internally (12-20 hours total). Catch it early (weekly fluid checks) and you can escape with cooler/radiator only (4-6 hours).
Estimated cost: $1,200-6,500
Driveshaft Center Support Bearing Failure
Occasional · medium severityTypical onset: 80,000-140,000 mi
Symptoms: Clunk or vibration from undercarriage during acceleration, Rumbling or grinding noise at highway speeds, Vibration worsens under load or when cold, Vehicle shudder during 30-50 mph acceleration
Fix: Two-piece driveshaft uses a rubber-isolated center bearing that deteriorates. Nissan issued a recall for some VINs, but many fall outside the range. Replacement requires dropping exhaust and driveshaft removal (2.5-4 hours). OEM part recommended as aftermarket bearings fail prematurely.
Estimated cost: $600-1,200
Transmission Mount Collapse
Common · medium severityTypical onset: 60,000-100,000 mi
Symptoms: Harsh clunk when shifting from Park to Drive or Reverse, Excessive driveline movement visible when rocking vehicle, Vibration through cabin at idle in gear, Transmission appears to sag when inspected from below
Fix: The hydraulic transmission mount fails internally, allowing excessive drivetrain movement. Common on both engine options due to weight and torque. Replacement requires supporting transmission and removing crossmember (2-3 hours). Use OEM mount only—aftermarket versions fail within 20k miles.
Estimated cost: $450-750
Fuel Filter Clogging from In-Tank Debris (V8 Models Especially)
Occasional · medium severityTypical onset: 80,000-130,000 mi
Symptoms: Rough idle and hesitation under acceleration, Intermittent stalling when fuel level drops below 1/4 tank, Check engine light with lean fuel mixture codes (P0171/P0174), Fuel pump whining noise from rear seat area
Fix: In-tank fuel filter on the pump assembly gets clogged from sediment, especially on V8s that consume more fuel. Filter is not separately serviceable—requires full fuel pump module replacement. Tank must be dropped (3-4 hours). Always replace both fuel level sensors at the same time as they fail from age.
Estimated cost: $800-1,400
VQ37VHR Timing Chain Guide Wear (3.7L V6)
Occasional · high severityTypical onset: 100,000-150,000 mi
Symptoms: Cold-start rattle from front of engine for 2-5 seconds, Metallic rattling at idle that increases with RPM, Check engine light with cam/crank correlation codes, Metal shavings in oil if guides have disintegrated
Fix: The VQ37 timing chain guides wear from oil starvation during cold starts or extended drain intervals. Requires front engine teardown with timing cover removal, all chains, guides, tensioners, and both VVT actuators (12-18 hours). Do both banks even if only one sounds bad. Catch it before catastrophic failure or you're looking at valve/piston damage.
Estimated cost: $3,500-5,500
The 3.7L V6 version is a decent buy if maintained obsessively and priced under market (timing chains are the main worry); avoid the 5.6L V8 entirely unless you have documentation of gallery gasket preventive service or can budget for catastrophic engine failure.
AI-assisted summary drawn from NHTSA recall data, our labor-times database, and platform knowledge. Not a substitute for a pre-purchase inspection on a specific vehicle.