Why is my Subaru Forester using so much fuel?
In most Forester cases, higher fuel consumption comes down to driving habits, maintenance needs, and added weight or aero drag rather than a mysterious defect. Simple adjustments and a quick tune‑up can often restore expected efficiency.
Common causes of increased fuel consumption
Several everyday factors routinely drag down mpg on a Subaru Forester. The following items are the most frequently cited by owners and technicians across model years.
Engine configurations and their impact
Subaru has used different powertrains in the Forester over the years. The widely used 2.5-liter four-cylinder with a CVT offers good efficiency in many conditions, but older turbocharged 2.0-liter variants and certain configurations can burn more fuel, especially with aggressive driving or under load. Understanding your exact engine and drivetrain helps set realistic expectations for mpg.
- Aggressive acceleration and high overall speeds, especially in city driving
- Excessive idling or frequent short trips that don’t let the engine reach optimal temperature
- Low tire pressure, uneven tire wear, or misalignment increasing rolling resistance
- Cargo load or roof-mounted gear (bike racks, cargo boxes) that creates aerodynamic drag
- Maintenance issues: dirty or clogged air filter, worn spark plugs, faulty oxygen sensor, dirty mass air flow (MAF) sensor, or clogged fuel injectors
- Fuel system or exhaust problems: evaporative system leaks, a loose or faulty fuel cap, or a restricted catalytic converter
- Older turbocharged variants or high-mileage engines may exhibit lower efficiency if not properly maintained
Concluding: While some variations are normal between model years and trims, most unexplained mpg drops come down to a combination of driving habits and maintenance. If mpg continues to fall despite addressing these factors, a diagnostic check can identify underlying sensor or exhaust issues.
How to diagnose and improve fuel economy in your Forester
Before you start, gather your recent fill-up data and note typical driving conditions. The steps below help you systematically diagnose and improve mpg, focusing on the most common culprits.
- Check tire pressure and wear: inflate to the level shown on the door placard and rotate if needed; underinflated tires can dramatically reduce fuel economy
- Reduce aerodynamic drag: remove roof racks or cargo boxes when not in use
- Improve driving habits: smooth acceleration, gradual throttle changes, steady speeds, and use cruise control on highways when appropriate
- Inspect air intake and filters: replace a dirty engine air filter and ensure there are no air leaks in the intake tract
- Assess ignition and fuel delivery: check spark plugs for wear and replace if needed; consider testing or replacing a faulty oxygen sensor or MAF sensor
- Evaluate the fuel system: use quality fuel and consider a professional fuel injector cleaning if symptoms (misfires, rough idle, or poor acceleration) appear
- Check evaporative (EVAP) system and fuel cap: ensure the cap seals properly and look for EVAP hose leaks or loose connections
- Inspect the exhaust and catalytic converter: a clogged or failing cat can sap MPG and performance; seek professional assessment if exhaust feels restricted or the engine runs unusually
- Review transmission and AWD-related maintenance: ensure CVT service intervals are followed (fluid level and condition) and that AWD operation isn’t unnecessarily engaged in dry conditions
- If mpg remains low, request a diagnostic: an OBD-II scan can reveal sensor faults or codes (like MAF, O2, or EVAP issues) that explain the drop and guide repairs
Concluding: Most drivers see the biggest gains from correcting simple maintenance items and adjusting driving habits. If you still see poor fuel economy after these steps, a qualified Subaru technician can perform a deeper inspection, including drivetrain and exhaust diagnostics.
Summary
The Forester’s fuel economy is influenced by engine choice, all-wheel-drive operation, and general vehicle load. By keeping tires properly inflated, minimizing aerodynamic drag, using smooth driving techniques, and staying on top of routine maintenance, most owners can restore or close the gap to the EPA estimates for their exact year and trim. For persistent issues, consult a Subaru service center for a targeted diagnostic and any needed repairs, using your model year’s specific fuel economy ratings as a baseline.
