What is 100,000 mile maintenance on a Subaru Forester?
At 100,000 miles, a Subaru Forester typically enters a major maintenance window. The exact tasks depend on whether your model uses a timing belt or a timing chain. In belt-driven engines, you usually replace the belt (and water pump) along with plugs, coolant, fluids, and filters. In chain-driven engines, there’s no fixed belt replacement, but a thorough inspection and fluid changes are usually advised. This milestone is about preventing wear-related failures and preserving reliability.
Engine design determines the 100k service path
Subaru’s Forester lineup spans multiple generations with different timing systems. Older models often used a timing belt on the 2.5-liter engine family, which requires replacement around 100,000 miles. Newer iterations use timing chains, which don’t have a fixed replacement interval but still benefit from a comprehensive 100k check of fluids, filters, and wear items.
What changes between belt and chain engines
For belt-driven engines, the 100k service commonly includes timing belt replacement plus related components, while chain-driven engines skip the belt replacement but still get major fluid and filter service and a general inspection. Both paths typically include spark plug changes and coolant service, plus routine inspections.
Belts and related belt-driven components are the core focus if your Forester uses a timing belt.
- Timing belt replacement, together with water pump, tensioners, and idlers; plus seals as needed.
- Spark plug replacement (often around 100,000 miles on many 2.5L engines).
- Coolant flush and replacement to protect the cooling system and keep the engine within spec.
- Transmission fluid service (CVT fluid in most modern Subarus) using the manufacturer‑recommended fluid.
- Differential/transfer case fluids (for AWD models) and general drivetrain lubrication checks.
- Brake fluid flush to maintain hydraulic brake performance and prevent moisture buildup.
- Engine air filter and cabin air filter replacement to keep intake and interior air clean.
- Accessory belt (serpentine belt) inspection and replacement if worn or cracked; plus hoses and clamps check.
- PCV valve inspection and general engine bay hose/connection checks.
- Battery health check and charging system inspection.
In contrast, chain-driven engines typically avoid a fixed timing-belt replacement interval. The 100k service for these models emphasizes fluids, filters, and a thorough inspection of the chain area, along with the same routine items listed above where applicable.
Chain-driven Foresters often focus on:
- Spark plug replacement (often around the same 100k mark, depending on model/year).
- Coolant flush and replacement.
- CVT or automatic transmission fluid change, using the Subaru‑spec NS-2 or equivalent fluid if applicable.
- Air filter and cabin filter replacement.
- Brake fluid flush and general brake system inspection.
- Serpentine belt inspection and replacement if worn, plus inspection of hoses and clamps.
- Visual timing chain/valve area inspection for unusual wear or noise during inspection, especially on older or high‑mileage examples.
- Battery health check and charging system inspection.
Regardless of engine type, you should also expect a comprehensive inspection of belts, hoses, exhaust, suspension, steering, and tires as part of the 100k assessment. This helps catch potential issues before they become roadside failures.
What to do next
Because exact tasks vary by model year, engine, and maintenance history, consult your owner’s manual and discuss with a Subaru technician to confirm the 100k maintenance plan for your Forester. Using OEM parts and documented service records can help maintain resale value and reliability.
Summary
At 100,000 miles, the Subaru Forester typically marks a major service milestone. If your model uses a timing belt, anticipate belt replacement (and water pump) plus plugs, coolant, and fluid/filter services. If your Forester uses a timing chain, the focus shifts to fluids, filters, belt/chain inspection, and a thorough overall inspection. In both cases, expect spark plug replacement, coolant refresh, CVT/automatic transmission fluid service, air and cabin filters, brake fluid flush, belt/hoses checks, and a battery/charging system check. Always verify exact requirements with your manual or dealer based on your year, engine, and maintenance history. Regular upkeep at this mile marker helps prevent failures and keeps your Forester running smoothly.
When should the timing belt be changed on a Subaru Forester?
Timing belt replacements:
Subaru timing belts need to be replaced after seven years or 105,000 miles; whichever comes first.
What year to stay away from a Subaru Forester?
You should generally stay away from Subaru Forester model years known for significant engine issues, such as the 1998–2001, 2003, 2006, 2009, and 2010 models due to head gasket failures and other problems. The 2011–2014 and 2014–2018 models are also problematic, particularly for excessive oil consumption, CVT transmission issues, and suspension problems, according to sources like Panda Hub, CoPilot for Car Shopping, CarBuzz, and MotorBiscuit.
You can watch this video to learn more about the worst model years for the Subaru Forester: 44sCar ExpertlyYouTube · Apr 14, 2025
Specific model years to avoid
- 1998–2001: These early models are known for frequent head gasket failures, which can be costly to repair.
- 2003 and 2006: These model years experienced recurring head gasket issues and other problems like electrical malfunctions and cooling system failures.
- 2009–2010: These years saw engine stalling, head gasket problems, and engine oil pipe ruptures. The 2010 model received particularly low reliability ratings.
- 2011–2014: The 2.5L engine (FB25) in these models is known for excessive oil consumption, which can lead to engine damage if not addressed. The 2011 model also had poor oil warning light design.
- 2014: Often cited as one of the worst model years, this model is known for severe oil consumption, CVT transmission problems, and broken coil springs.
- 2015: Continued issues with engine and transmission troubles were reported, along with airbag sensor malfunctions.
- 2018: Recall issues related to faulty rear suspension springs and engine valves affected some models.
Common issues across multiple years
- Head gasket failure: A common issue in many pre-2012 models, especially those with the 2.5L EJ series engine, typically occurring around 60,000 to 100,000 miles.
- Excessive oil consumption: A major problem in models with the newer FB25 engine from 2011 to 2014, which can cause serious engine damage.
- Transmission issues: The 2014 model's CVT transmission was prone to problems, and the 2015 model also had reports of transmission troubles.
- Suspension and wheel bearings: Problems with rear suspension springs and premature wheel bearing wear were reported in some models, including the 2014.
- Cracking windshields: A widespread issue across multiple model years, including the 2014 and 2017, which even led to a class-action lawsuit.
What to look for when buying a used Forester
- If considering an older model (1998-2012), check for documented evidence of head gasket replacement, preferably with upgraded multi-layer steel gaskets.
- For 2011-2014 models, be aware of excessive oil consumption and ensure the owner is diligent about checking oil levels. If possible, check the VIN for any service bulletins or extended warranty coverage related to oil consumption.
- If looking at a 2014 or newer, get a pre-purchase inspection, with a specific focus on the transmission and suspension.
- Look for rust, especially in areas with heavy road salt use.
How much should a 100,000 mile service cost?
The average cost of a 100k service is $500-$800 but can vary widely based on the specific procedures needed and local labor rates. Premium fluids and parts increase costs too. In general, you can expect to pay more for 100k over a standard oil change.
What needs done to a Subaru at 100,000 miles?
100,000 Miles
The 100,000-mile maintenance interval is another extensive one. For this one, the 10,000- and 20,000-mile service items are combined. Additionally, the spark plugs, transmission fluid, and differential fluid are all replaced.
