2018 Subaru Forester Battery: Group Size, CCA & Replacement Options
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Quick answer
- BCI Group Size: Group 35
- Cold Cranking Amps (CCA): 390-550 CCA
- Reserve Capacity (RC): 80-100 minutes
- Battery Type: AGM required for models with auto start-stop; standard flooded for others
- Terminal Layout: Left-hand positive
- Dimensions (L x W x H): 9 1/16" x 6 7/8" x 8 7/8"
Replacement battery options
- Interstate: MTX-35 or MTP-35
- DieHard: Gold 35 or Platinum AGM 35
- Optima: YellowTop DH6
AGM vs flooded — which does this vehicle need?
If your 2018 Forester has the auto start-stop feature, you must use an absorbed glass mat (AGM) battery. These are designed for the frequent, deep cycling that start-stop systems demand. Using a standard flooded battery in a start-stop vehicle will result in a very short service life.
If your Forester does not have auto start-stop, you can use either a standard flooded battery or an AGM. An AGM will still offer benefits like longer life, better vibration resistance, and more consistent power delivery, but it is not strictly required.
Post-installation relearn / reset procedure
After replacing the battery on a 2018 Subaru Forester, you may need to perform a relearn procedure for the power window auto up/down feature. To do this, simply roll each window down and then hold the "up" switch until the window is fully closed. This will reset the memory for each window.
No other major relearn procedures are typically required, though it may take a few drive cycles for the engine computer to recalibrate fuel trims.
Signs of a failing battery
- Slow engine cranking, especially on cold mornings
- Dimming headlights when the engine is off
- A clicking sound when you turn the key
- The battery warning light is illuminated on the dashboard
- Corrosion around the battery terminals
Common battery issues for this generation
The 2014-2018 Subaru Forester generation is known for having a parasitic draw on the battery from the CAN bus system, which can cause the battery to drain prematurely. If you frequently have a dead battery even after replacing it, you may need to have a technician diagnose a parasitic draw.
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More specs for the 2018 Subaru Forester
Oil Capacity & Filter
Capacity, weight, filter PN, drain plug torque, change interval.
Fluid Type Specs
Engine oil, coolant, ATF, diff, brake, PS, DEF — with OEM spec numbers.
Coolant Capacity & Type
Total system capacity, OEM coolant spec, flush interval, bleed tips.
Transmission Fluid & Service
Trans model, fluid spec, capacity, filter PN, service interval.
Torque Specifications
Lug nuts, drain plug, caliper, axle nut, plug, key fasteners.
Brake Pad & Rotor Specs
Pad PNs, rotor size, min thickness, caliper torque.
Tire Size & Pressure
OEM size, cold psi, bolt pattern, wheel size, TPMS.
A/C Refrigerant & Oil
R-134a or R-1234yf, charge oz, PAG oil spec.
Bulb Sizes (Headlight, Tail, Fog)
Headlight, fog, tail, turn, reverse, interior.
Factory Maintenance Schedule
Service intervals by mileage, severe-duty notes, known issues.
Towing Capacity & Payload
Max tow, payload, GVWR/GCWR, hitch class by trim.
Fuse Box Diagram & Amperage
Fuse box locations, layout, amps, and what each fuse controls.
Serpentine Belt Routing & Length
Belt routing, length, rib count, OEM + aftermarket PNs.
Wheel Alignment Specifications
Camber, caster, toe ranges (front & rear), adjustability notes.
Paint Color Codes
All factory colors with paint codes, sticker location, touch-up tips.
Wiper Blade Sizes
Driver/passenger/rear blade size, attachment, OEM + cross-refs.
Spark Plug Type & Gap
Plug PN, gap, torque, interval by engine.
Transmission & Axle Gear Ratios
Trans gear ratios, axle ratios, RPO codes, tow vs MPG impact.
Key Fob Programming
DIY programming steps, FCC ID, fob PN, battery, transponder.
Same spec — other model years
Maintenance & repair guides
2018 Subaru Forester Maintenance Schedule →
Available maintenance guidance; confirm the manufacturer schedule.
Repair planning references →
Plan the scope of work; detailed procedures need configuration-matched evidence.
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