Toyota Voxy: 1AZ-FSE D-4 Fuel Dilution of Engine Oil

During cold starts the 1AZ-FSE D-4 engine enriches the fuel mixture and retards injection timing to aid warm-up. Unburned fuel puddles on cold cylinder walls and migrates past piston rings into the sump, diluting engine oil with petrol. Repeated short cold trips compound the effect, reducing oil viscosity well below its rated grade and accelerating bearing and piston wear. The problem is most severe in vehicles used predominantly for short urban journeys.

• Petrol smell detectable on the oil dipstick
• Oil level rising above the maximum mark without any top-ups
• Thin or watery oil texture on the dipstick
• Increased engine wear if not addressed by shortened service intervals

1. 1

   Pull the dipstick and smell for fuel contamination — oil should smell like oil, not petrol.

2. 2

   Check whether the oil level reads above maximum without any top-ups having been performed.

3. 3

   Review service records for oil change intervals; vehicles used for short trips should show intervals shorter than 5,000 km.

4. 4

   Cold-start a known history vehicle and check for excessive white or rich exhaust smoke.

$150 to $600 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.

• “What was the typical journey length this vehicle was used for daily?”
• “Were oil changes done more frequently than the factory-specified interval?”

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.