# Subaru Head Gasket Failure and Water in Oil — New Zealand Guide

> Subaru EJ-series engines have a known head gasket vulnerability. Coolant in oil is a common consequence. Here is what New Zealand Subaru owners need to know.

- Canonical URL: https://www.eek.nz/news/subaru-water-in-oil-head-gasket-nz
- Published: 2026-04-07
- Author: EEK Mechanical
- Publisher: EEK Mechanical, a trade name of Forman Pacific, LLC

## Subaru's EJ Engine Head Gasket History

The Subaru EJ-series engine, fitted to Impreza, Legacy, Forester, and Outback models from roughly 1989 to 2012, has a well-documented head gasket vulnerability. Particularly affected are the non-turbo EJ20 and EJ25 engines from the late 1990s and early 2000s. The design uses composite multi-layer steel gaskets that are susceptible to failure between coolant and oil passages, leading to coolant contaminating the oil system.

## Signs Specific to Subaru

Subaru coolant-in-oil can be subtle at first. Look for: a slight sweet smell from the engine bay; oil filler cap with a grey milky residue inside; coolant level dropping slowly with no visible external leak; and a slight white haze in the exhaust after the engine warms up. By the time the dipstick shows obviously milky oil, the contamination is typically significant.

## Cost of Running on Contaminated Oil

The EJ engine has aluminium cylinders with a cast-iron liner — the bearing surfaces are particularly sensitive to lubrication quality. Running the engine with coolant-contaminated oil accelerates wear on the big-end and main bearings, potentially converting a significant cost head gasket job into a significant cost-6,000 engine rebuild.

## What to Do

If your Subaru shows any of these signs, stop and call EEK Mechanical. We manufacturer-spec fuel system recovery the oil system, provide documentation for the mechanical repair, and can refer you to Subaru specialists experienced with EJ head gasket work.

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Source: https://www.eek.nz/news/subaru-water-in-oil-head-gasket-nz