Subaru Forester: EJ20 Excessive Oil Consumption from Piston Ring Gap

EJ20 engines in SG and SH Foresters consume engine oil at rates well above Subaru's own published acceptable limit due to piston ring end-gap tolerances that are too wide from the factory, combined with ring flutter in the boxer (horizontally-opposed) orientation. The horizontal cylinder orientation allows oil to pool on the lower piston ring during idle and low-load running, which the rings then fail to fully control under acceleration. Consumption is accelerated by infrequent oil changes that allow oil to thicken and varnish the ring lands, causing the rings to stick partially open. Affected engines may consume 1 litre per 1,000 km or more.

• Oil level dropping by 1 litre or more between 5,000 km service intervals with no external leak visible
• Blue-grey smoke from the exhaust on startup after the car has sat overnight, clearing after a minute of running
• Blue smoke visible from the exhaust during hard acceleration or engine braking (overrun), particularly when the oil level is low
• Spark plugs showing oil fouling or black carbon deposits on the electrode when inspected

1. 1

   Check oil level at the dipstick and note whether it has been recently topped up to mask consumption.

2. 2

   Ask for service history showing how often oil was required between changes.

3. 3

   Perform a cold-start observation for blue exhaust smoke.

4. 4

   Remove spark plugs and inspect for oil fouling.

5. 5

   If a workshop inspection is possible: A compression test combined with a leak-down test can confirm ring seal; low compression with high leak-down (particularly with air escaping into the crankcase) indicates ring wear.

$2,800 to $5,500 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.

• “How many litres of oil have been added between the last two service intervals, and do you have receipts?”
• “Does the car ever smoke at startup or under hard acceleration?”
• “When were the spark plugs last replaced and what condition were they in?”

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.