What causes high fuel consumption in a Subaru Forester?

High fuel consumption in a Subaru Forester is typically caused by a combination of driving habits, added load or aero drag, and maintenance issues, amplified by the model’s all-wheel-drive system.

Understanding the question in context

The Forester is designed for versatility and capability, not maximum fuel efficiency. Several factors—ranging from how you drive and what you carry to the vehicle’s mechanical condition and environmental conditions—can push real-world mpg above the EPA estimates. Below is a structured look at the main contributors and how to address them.

Driving style and vehicle load

How you drive and what you haul or carry has a direct impact on fuel economy. The following items are common, easily adjustable factors that raise fuel use in daily use.

Factors tied to driving behavior and how you load the vehicle.

• Aggressive acceleration and high-speed driving


• Frequent rapid braking or extended idling in traffic


• Carrying extra weight—passengers, cargo, or added gear


• Roof racks, cargo boxes, or bike mounts that increase aerodynamic drag


• Short trips and cold starts that keep the engine in inefficient temperature ranges


• Using air conditioning aggressively in warm weather, especially in stop-and-go traffic

In short, how you drive and how much you carry are the biggest, adjustable contributors to Forester fuel burn.

Maintenance, mechanical condition, and fuel delivery

Maintenance issues and component wear can quietly degrade efficiency. If any of these parts aren’t performing well, you may see higher fuel use before other symptoms appear.

Possible mechanical and system-related causes to check.

• Underinflated tires or uneven tire wear


• Dirty or clogged air filter reducing engine efficiency


• Faulty oxygen (O2) sensor or mass air flow (MAF) sensor causing poor fuel metering


• Misfiring spark plugs or ignition problems


• Exhaust restrictions, including a partially clogged catalytic converter


• Dirty fuel injectors or fuel delivery issues


• Transmission issues in CVT-equipped models, such as slippage or poor gear ratio optimization


• Incorrect engine oil grade or excessive engine oil viscosity

Maintenance health is a frequent, fixable driver of inefficiency; addressing these issues can restore expected fuel economy.

Vehicle design factors, equipment, and operating environment

Some design choices and environment-specific factors inherently affect fuel use. Forester characteristics and common aftermarket add-ons can push consumption higher in everyday use.

Notes on design and operating environment that influence efficiency.

• All-wheel drive (Symmetrical AWD) is standard on most US Foresters and increases rolling resistance versus two-wheel drive configurations


• Vehicle weight varies by trim, typically adding to engine load compared with smaller SUVs


• Roof rails, roof racks, or a bulky roof cargo box significantly raise aerodynamic drag


• Rough terrain, off-road use, or frequent use of traction control can raise energy use


• Cold weather and short trips prolong engine warm-up time, reducing efficiency


• Higher highway speeds reduce efficiency due to aerodynamic drag

In short, the Forester’s capability-focused design and typical accessory usage can elevate fuel consumption under real-world conditions.

Model variations and regional differences

Fuel economy can vary by year, market, and trim. Some generations offered mild-hybrid or differing drivetrain calibrations in certain regions, which can affect efficiency compared with standard gasoline models in other markets.

Notes on configuration differences that affect economy.

• Some markets have mild-hybrid (e-Boxer) or hybrid variants that differ in fuel economy from non-hybrid models


• CVT tuning and AWD implementations can vary across model years and trims, influencing real-world mpg


• Engine updates or emissions-control changes can alter fuel consumption between generations

The exact causes of higher fuel use can depend on your Forester’s year, region, and configuration.

What to do if your Forester isn’t getting expected fuel economy

If you notice a sustained drop in efficiency, start with a practical check of key factors you can control, then consider professional diagnostics for less accessible issues.

Actionable steps to improve or diagnose fuel economy.

• Check and maintain proper tire pressure per manufacturer specifications; rotate tires as recommended


• Remove unnecessary cargo and limit aero-drag items on the roof


• Keep engine air intake clean (replace air filter as needed) and address sensors that may be faulty


• Schedule maintenance according to Subaru’s timetable, paying attention to CVT service if applicable


• Ensure the exhaust system is clear; investigate any signs of reduced performance or check engine lights


• Monitor fuel economy over several tanks and note any patterns (city vs highway) to pinpoint likely causes

Persistent, unexplained fuel economy declines warrant a professional diagnostic to assess the engine, transmission, and emissions systems.

Summary

High fuel consumption in a Subaru Forester generally arises from a combination of driving habits, load and aero drag, maintenance quality, and the model’s all-wheel-drive design. By optimizing driving behavior, removing unnecessary weight, keeping tires and maintenance up to date, and checking for sensor or exhaust issues, you can recover expected efficiency. If problems persist, consult a qualified technician to diagnose potential drivetrain or emission-system faults and to verify that your particular Forester matches the manufacturer’s performance targets.

Why is my Subaru Forester getting bad gas mileage?

Checking the tire pressure and have the alignment checked on regular basis can help prevent this problem. Defective Fuel Pump: Fuel delivery issues can drastically affect fuel efficiency. The fuel pump pulls fuel from the gas tank to the fuel injectors. The fuel pump can become clogged or malfunction.

Why is my Subaru consuming more fuel?

High fuel consumption in your Subaru can be caused by a number of factors, from tire pressure to driving habits. By addressing these issues, such as maintaining your tires, replacing clogged filters, and driving smoothly, you can improve your Subaru's fuel efficiency.

What is the most common problem with the Subaru Forester?

The most common problem with the Subaru Forester is the continuously variable transmission (CVT), which can suffer from issues like shuddering, delayed acceleration, and whining noises, and may require expensive repairs. Other frequent issues include problems with the engine (especially oil consumption), the electrical system, and, in certain model years, issues with windshields cracking and batteries dying quickly.
 
You can watch this video to learn more about Subaru Forester common problems: 51scar PROblemsYouTube · Feb 19, 2024
Transmission (CVT)

• Shuddering and jerking: This often occurs when accelerating from a stop.
• Delayed acceleration and slipping: The engine revs up but the car doesn't speed up as expected, which can be dangerous when merging.
• High-pitched whining: This can be a sign of worn pulley bearings inside the transmission.
• Repair cost: CVTs are often not rebuildable and require a complete, expensive replacement. 

Engine

• Excessive oil consumption: Many model years, particularly from the 2014-2018 generation, are known for burning through oil rapidly.
• Oil leaks: Leaks, often requiring expensive engine replacements, are another reported problem. 

Electrical and other issues

• Electrical malfunctions: Issues can range from infotainment system glitches and GPS errors to more serious problems like a battery dying prematurely or the EyeSight safety system turning off unexpectedly. 
• Air conditioning (AC): Some models experience AC failure that can be costly to fix. 
• Windshields: In the 2019-2024 generation, windshields can crack from small chips. 
• Airbag malfunctions: Older models, such as the 2009-2011, have been associated with malfunctioning airbags. 

This video explains some of the most common issues with the Subaru Forester, including the transmission and engine: 57sGear GazetteYouTube · Oct 23, 2025

How do I fix high fuel consumption?

To fix high fuel consumption, combine proper maintenance (like checking tire pressure and replacing air filters) with fuel-efficient driving habits (such as accelerating smoothly and avoiding high speeds). Keeping your vehicle well-maintained and driving smartly will help reduce unnecessary fuel use. 
You can watch this video to learn how to improve fuel consumption while driving: 39sCar Care CluesYouTube · Dec 27, 2024
Vehicle maintenance and checks

• Check tire pressure: Keep tires properly inflated to reduce rolling resistance and improve fuel economy. 
• Replace air filters: A clogged air filter restricts airflow, forcing the engine to use more fuel. 
• Perform regular maintenance: Follow the manufacturer's maintenance schedule, including regular oil changes. Ensure your spark plugs and fuel injectors are in good condition. 
• Address issues with sensors: Faulty oxygen or mass air flow (MAF) sensors can negatively impact fuel consumption. 

Driving habits

• Accelerate and brake gently: Avoid hard acceleration and sudden braking. Accelerate smoothly and anticipate stops to brake lightly. 
• Maintain a steady speed: Avoid excessive speeding and use cruise control on long, flat stretches of highway to maintain a consistent speed. 
• Reduce idling time: Turn off your engine if you're going to be parked for more than a minute. 
• Minimize weight: Remove any unnecessary heavy items from your trunk or car. 
• Improve aerodynamics: Keep windows closed at higher speeds, as open windows increase drag. 

This video explains other common reasons for high fuel consumption: 1mThe Auto BrainYouTube · May 3, 2025
Additional tips

• Plan your routes: Combine errands to make fewer trips. 
• Avoid aggressive driving: Drive in a predictable and smooth manner to save fuel. 
• Keep windows closed at high speeds: Opening windows at speeds above 45 mph increases fuel consumption.