Infiniti G35: VQ35DE Intake Valve Stem Seal Wear & Oil Consumption

The VQ35DE DOHC V6 uses intake valve stem seals made from a rubber compound that hardens and shrinks with age and heat cycling. At high mileage — typically above 130,000 km — the seals no longer wipe the intake valve stem effectively, allowing engine oil to be drawn down the valve guide into the combustion chamber during the intake stroke's vacuum pulse. The result is measurable oil consumption (commonly 0.5-1.5 litres per 1000 km in severe cases) and blue smoke on overrun or after long idle periods. The condition is worsened if the engine has run low on oil. Repair requires removal of the cylinder heads to replace all 12 intake valve stem seals, making it a significant workshop job.

• Blue or blue-grey smoke from exhaust on overrun or when accelerating after long idle
• Oil consumption exceeding 500 ml per 1000 km between services
• Oil level dropping noticeably between service intervals with no external leaks
• Fouled spark plugs with oily carbon deposit on electrode, particularly on inner cylinders

1. 1

   Check engine oil level against the dipstick and compare to the last service record — a shortfall with no visible external leaks points to oil consumption.

2. 2

   Rev the engine hard then lift off and watch the exhaust for blue smoke puff on overrun.

3. 3

   Pull at least one spark plug from each bank and inspect for oil fouling or heavy carbon.

4. 4

   Ask specifically how often oil is topped up between services.

Parts involved: Cylinder head.

$1,600 to $3,800 at New Zealand independent workshop rates. That is for this job on its own, not for the car.

An estimate, in NZD, for the repair as normally carried out. What a specific car costs depends on which part has failed and what it damaged on the way — treat this as the floor for a negotiation, not a quote.

• “Does the car use any oil between oil changes and how much?”
• “Has there ever been blue smoke from the exhaust on deceleration?”
• “When were the spark plugs last replaced and did they show oil fouling?”
• “Has any valve stem seal or head gasket work been performed?”

The failure described above is documented in published sources — owner forums, technical service bulletins, recall notices and workshop write-ups — held in our fault database. The inspection instructions and the cost estimate are KickTyres’ own interpretation of them, and it is a starting point for an inspection rather than a manufacturer statement.