Most Foresters aren’t unusually thirsty, but higher fuel use is common and usually caused by a mix of driving style, maintenance needs, and added drag. This guide explains the main reasons and practical steps to diagnose and fix them.
Common causes of higher fuel consumption
Several everyday factors can push a Forester’s fuel economy down. The all-wheel-drive system, the CVT or another transmission pairing, aerodynamics with roof cargo, and maintenance condition all play a role. The following list highlights the most frequent culprits you can check yourself or with a quick service visit.
- Aggressive driving and frequent rapid acceleration or hard braking
- Lots of short trips and frequent cold starts, which keep the engine in less efficient ranges
- Added drag from roof racks, cargo, bicycle racks, or heavy loads
- Underinflated tires, poor wheel alignment, or worn tires increasing rolling resistance
- Maintenance items such as a dirty air filter, faulty oxygen sensor, or dirty mass airflow sensor
- Low-quality or wrong-octane fuel, or fuel system issues that prevent optimal combustion
- Engine or exhaust problems such as EVAP leaks or a clogged catalytic converter
- Model-related factors: all-wheel drive with a CVT and heavier weight can reduce highway efficiency vs. two-wheel-drive setups
Taken together, these factors explain why your Forester might seem unusually fuel-hungry. Identifying which are affecting your specific vehicle helps you target fixes effectively.
What to check and how to fix these issues
Begin with quick, low-cost checks and then move to targeted maintenance or professional diagnostics if needed. The steps below are arranged to minimize expense while maximizing the chance of a meaningful improvement.
- Perform a quick maintenance check: replace a dirty air filter, inspect spark plugs and ignition coils, and have a mechanic test the mass airflow sensor and oxygen sensors. Address any diagnostic trouble codes (DTCs) you may see.
- Check tires and vehicle load: inflate tires to the manufacturer-recommended pressure, rotate if needed, and remove roof racks or non-essential weight when not in use. Misaligned or worn tires can dramatically raise rolling resistance.
- Assess driving habits: smooth, steady acceleration, gradual braking, and maintaining a steady speed on highways can improve efficiency. Use cruise control on long highway stretches when appropriate.
- Do a diagnostic check: use an OBD-II scanner to look for misfires, abnormal fuel trim, or EVAP system faults. Resolve any issues or leaks indicated by the scan.
- Inspect exhaust and fuel-system health: if a converter is partially clogged, injectors are dirty, or there are vacuum leaks, efficiency will suffer. Have these components tested and serviced as needed.
If fuel use remains high after completing these steps, consider a professional diagnostic at a Subaru dealer or trusted shop. Some issues, such as EVAP leaks or catalytic converter problems, require specialized equipment to diagnose and repair accurately.
Model-specific considerations
While the guidance above applies to most Forester models, certain variants can influence fuel economy more than others. Knowing your year and drivetrain helps set realistic expectations and prioritize fixes.
All-wheel drive and transmission impact
Foresters with standard AWD and a continuously variable transmission (CVT) typically show lower efficiency in city driving and with heavy loads, though highway efficiency can still be good. Consistent maintenance of the CVT fluid and timing of any service interval recommended by Subaru can help preserve mpg.
Turbo and older configurations
Earlier or higher-performance Forester variants with turbo engines or different transmissions may have different fuel-economy ranges. If you own a turbo model or an older generation, slight changes in fuel economy are common due to engine design and operating characteristics.
Summary
Most increases in Forester fuel consumption stem from driving style, maintenance needs, and added drag. Start with simple checks—air filters, tire pressure, and routine service—then review driving habits and run a diagnostic scan if needed. For persistent issues, a professional inspection can identify EVAP leaks, sensor faults, or exhaust restrictions that are harder to diagnose at home. With targeted checks and mindful driving, you can restore efficiency and keep fuel costs in check.