Subaru Impreza: EJ25 turbo ringland failure

The turbocharged EJ25 (as fitted to WRX STi variants on GD/GG platform) is prone to ringland failure on pistons 2 and 3 under sustained high-boost conditions. The flat-four firing order concentrates heat on centre cylinders. Factory ring land bridges are relatively thin and crack under detonation or lean conditions. This is well-documented across the global STi community and affects both stock and modified cars, though the risk increases sharply with boost, ethanol blends, or tuning beyond OEM parameters. Failure results in catastrophic oil consumption and blue smoke.

• Sudden excessive blue or grey smoke under acceleration
• Severe oil consumption (more than 1L per 1000km)
• Loss of power on cylinders 2 or 3
• Compression test showing low or zero compression on one cylinder
• Knocking or rattling at idle after oil loss

1. 1

   A healthy EJ25 turbo should show 150–180 psi with less than 10% variation between cylinders.

2. 2

   Check dipstick and note oil colour; check for blue smoke at tailpipe under load.

3. 3

   Review service history for oil change intervals — neglected oil is a contributing factor.

4. 4

   Ask if the car has been mapped or run on E85.

5. 5

   If a workshop inspection is possible: Perform a wet and dry compression test on all four cylinders before purchase.

Parts involved: Turbocharger.

$4,500 to $9,500 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.

• “Has the car ever been tuned or run on E85 fuel?”
• “Has it been compression tested recently?”
• “What oil type and change interval has been used?”
• “Has the engine ever been rebuilt or had any internal work?”

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.