Holden Commodore Water in Oil — V6 and V8 Contamination Issues

The V6 Intake Manifold Gasket Problem

The Holden Ecotec V6 — fitted to VT, VX, VY, and VZ Commodores — has an intake manifold that carries coolant. When the plastic intake manifold gaskets fail, coolant can drip directly into the lifter valley and sump, mixing with engine oil. This was a widespread problem on high-mileage NZ examples and is well-documented in the Holden community.

Signs in a Commodore V6

Look for a milky or brown residue inside the coolant overflow reservoir; coolant level dropping without a visible external leak; a slight oily film on top of the coolant; and milky deposits on the oil filler cap. External coolant leaks are also common with this failure — a puddle of coolant under the car does not rule out internal contamination.

LS V8 — Robust but Not Immune

The Gen III and IV LS V8 engines fitted to VZ, VE, and VF Commodores are significantly more robust. Water-in-oil on an LS is almost always flood-related or caused by a failed oil cooler (less common). Head gasket failure on a stock LS is rare unless the engine has severely overheated.

Service and Documentation

EEK Mechanical carries out oil system decontamination for Commodores across New Zealand. We provide written reports for insurance purposes or for mechanics quoting head gasket or intake manifold repairs.