How do I stop my Subaru from burning oil?
Oil burning in Subarus is often fixable by addressing the PCV system, sealing leaks, and using the correct oil; more stubborn cases may require engine service or an overhaul.
What typically causes oil burning in Subarus
Subaru engines can burn oil for several reasons. Common culprits include a sticking or clogged PCV valve and associated hoses, worn valve stem seals, and worn piston rings or oil-control rings. Turbocharged models may develop oil leakage from turbo seals. External leaks from valve covers, gaskets, or oil lines can also cause oil loss that appears as burning oil when it hits hot exhaust components. Misfiring engines or using the wrong oil grade can contribute as well. A proper diagnosis usually starts with a PCV and leak check, followed by engine health tests if needed.
Diagnostic steps to identify the source
The following steps help determine whether the issue is a simple system fault or deeper engine wear.
Interpreting symptoms and planning tests
Blue smoke on startup or under acceleration often points to burning oil in the combustion chamber, while oil smell at startup can indicate leaks or pouring oil into the exhaust. Track oil consumption over a defined distance and inspect exhaust smoke, oil level, and dipstick consistency to guide your next moves.
- Track oil consumption: record how many quarts you add over a set distance (e.g., per 1,000 miles) and notice if blue smoke accompanies starts or hard acceleration.
- Inspect the PCV system: locate and replace a clogged or stuck PCV valve; inspect vacuum hoses for cracks or disconnections and replace as needed.
- Check for external leaks: inspect valve cover gaskets, oil pan gaskets, turbo oil lines (on turbo models), and other seals for seepage.
- Assess engine health: remove and inspect spark plugs for oil fouling; perform a compression test or leak-down test to gauge piston/ring and valve seal condition.
- Evaluate turbo seals (if applicable): look for oil in the intercooler or intake along with excess exhaust smoke that could indicate turbo oil leakage.
Conclusion: A structured diagnostic helps distinguish simple PCV or leak issues from deeper engine wear that requires more extensive repairs.
Fixes and treatment by likely cause
Actions range from inexpensive maintenance to major engine work. This guide lists approaches from least invasive to most extensive, based on what the diagnostic steps reveal.
Least invasive fixes and preventive steps
- PCV system maintenance: replace the PCV valve, inspect and replace cracked or clogged hoses, and ensure there are no vacuum leaks. A healthy PCV system is a frequent cure for oil consumption.
- Seal and gasket replacements: replace worn valve cover gaskets and inspect oil filter housing and oil lines for leaks; fixing leaks can dramatically reduce apparent oil burning.
- Turbo-related checks (turbo models): if oil is leaking into the intake or exhaust due to turbo seals, service or replace the turbo as needed.
- Oil specification and maintenance: verify you are using the correct oil viscosity and specification (often synthetic 0W-20 for many modern Subarus) and adhere to the manufacturer’s oil-change interval. Avoid mixing oils and use quality filters.
Conclusion: In many cars, these steps resolve the issue without major engine work, and they should be performed before considering deeper repairs.
Major repairs and engine wear scenarios
- Piston rings and oil-control rings wear: significant oil consumption due to ring wear typically requires engine rebuilding, a new short block, or other substantial bottom-end work. This is the most invasive fix and can be costly.
- Valve stem seals and head-work: worn valve seals can cause oil to burn into the cylinders; replacing seals may involve head service or more extensive work depending on engine design and mileage.
- Turbocharger replacement (turbo models): if turbo seals are the source of oil loss, replacing or rebuilding the turbo may be necessary.
- Warranty and service programs: some model years have service bulletins or extended coverage for oil consumption issues; check with your Subaru dealer for current coverage and recalls.
Conclusion: If diagnostic results point to internal engine wear, a professional assessment is essential to determine whether a repair, rebuild, or engine replacement is the best path forward. Proactive communication with a Subaru-certified technician helps you understand options and costs.
Preventive maintenance to reduce future oil burning
Adopting prudent maintenance habits can minimize future oil consumption problems and help you catch issues early.
- Use the oil grade and specification recommended by Subaru for your model and climate (typically synthetic 0W-20, but verify in your owner’s manual).
- Change oil regularly and preferably at or before the recommended interval, especially if you do lots of short trips or live in extreme temperatures.
- Keep the PCV system clean and functioning; replace the PCV valve and hoses as part of routine maintenance.
- Choose quality oil filters and reputable brands; avoid mixing different oil viscosities or using low-grade oils that don’t meet spec.
- Address blue smoke or oil smells promptly to prevent catalytic converter damage and to identify issues early.
Following these practices helps protect engine health and reduces the likelihood of recurring oil consumption problems.
Summary
Stopping oil burning in a Subaru starts with a methodical diagnosis focused on the PCV system, leaks, and oil quality. Many cases improve with inexpensive fixes like PCV valve replacement and gasket repairs, while others reveal deeper engine wear that requires more intensive work such as a piston-ring rebuild or head/service. Use the manufacturer’s recommended oil and maintenance schedule, monitor oil usage, and consult a Subaru-trained technician if consumption remains high. With careful diagnosis and timely maintenance, you can restore engine performance and curb oil loss.
