What are Subaru pistons made of?

Subaru pistons are made from aluminum alloy; in modern engines the exact type—whether forged or cast—depends on the engine family and year. In general, performance-oriented or turbocharged Subaru engines tend to use forged aluminum pistons for strength and weight savings, while some earlier or cost-focused designs used cast aluminum.

Across Subaru’s lineup, piston material and manufacturing methods have evolved to address heat, load, and efficiency needs. The EJ, FA, and FB engine families illustrate how Subaru balances durability, performance, and production cost by choosing forged versus cast pistons and applying coatings or finishes as appropriate for the intended duty cycle.

Piston materials at a glance

Before listing the typical approaches, it’s helpful to note the overall categories Subaru has used across its engines.

• Aluminum alloy pistons are standard in Subaru engines across multiple generations and configurations.


• Forged aluminum pistons are common in modern, high-performance, or turbocharged variants to maximize strength while keeping weight down.


• Cast aluminum pistons appear in some older or non-turbo designs where lower cost and simpler manufacturing are prioritized.

The exact choice—forged versus cast and any coatings—varies by engine family and model year, reflecting Subaru’s design goals for each application.

Coatings and design features

Before diving into specifics, this section explains how coatings and geometry complement piston material to manage heat, wear, and efficiency.

• Low-friction coatings on piston skirts or crowns help reduce wear and improve fuel efficiency.


• Optimized piston-ring land geometry and thermal management features are tailored to each engine family, including turbocharged versus naturally aspirated designs.


• Some pistons in performance-oriented Subaru engines may include coatings to better resist high temperatures and knock risk associated with boost.

In practice, Subaru engineers tailor the piston package to the engine’s expected duty cycle, boost level, and reliability targets, balancing cost, weight, and longevity.

Why piston design matters for Subaru engines

Piston material and manufacturing choices influence durability under high RPM, sustained load, and turbocharged operation. Forged aluminum pistons generally offer higher strength-to-weight ratios and better resistance to detonation under boost, while cast aluminum pistons can be sufficient for lower-stress, non-turbo applications.

Summary

Subaru pistons are predominantly aluminum alloy, with the manufacturing approach (forged or cast) and any coatings varying by engine family and year. Forged aluminum pistons are common in modern and turbocharged Subaru engines for improved strength and weight savings, while cast aluminum pistons remain in certain older or non-turbo designs. This variation reflects Subaru’s aim to balance performance, durability, and cost across its vehicle lineup.

Are forged pistons steel or aluminum?

Forged pistons are created by placing a heated billet of aluminum alloy into dies that form the billet into shape via high compressive force in a press.

Why are Subaru pistons different to other cars?

Subaru firmly believes that the Horizontally-Opposed Engine is the optimum design for driving enjoyment. The pistons face away from each other in a 180º symmetrical layout around the crankshaft and work to balance out each other's vibrations, delivering a smooth, shudder-free feel.

Are Subaru engines cast iron?

Aluminum alloy blocks with cast iron cylinder liners enhance reliability and extend engine life. The large-capacity air cleaner with dual elements protects the engine from dust and debris.

What material are car pistons made of?

Engine pistons are most commonly made of aluminum alloys due to their lightweight properties, high thermal conductivity, and low manufacturing cost. For high-performance or heavy-duty applications, pistons can be made from forged aluminum or forged steel. Older engines, or specific commercial vehicles, may also use cast iron.
 
This video explains how pistons work inside an engine: 39sHistory of Simple ThingsYouTube · May 25, 2025
Common materials

• Aluminum alloy: The most common material for modern pistons in both gasoline and diesel engines. 
  • Pros: Lightweight, which reduces the engine's overall mass and allows for quicker acceleration. They have excellent thermal conductivity, helping to dissipate heat efficiently. 
  • Cons: Can lose strength at high temperatures, and their higher thermal expansion rate requires more clearance between the piston and cylinder wall. 
  • Subtypes:
    • Cast aluminum alloy: Produced by pouring molten alloy into a mold. This is the most common type for standard passenger cars, notes Quora. 
    • Hypereutectic aluminum alloy: An alloy with a high silicon content (over 11%) which increases wear resistance and strength. 
• Cast iron: An older material used in some engines from the past and in certain commercial vehicles. 
  • Pros: It is a strong and durable material. 
  • Cons: Its high density makes it less ideal for modern, high-revving engines where weight reduction is a priority, says Quora. 

High-performance materials

• Forged aluminum: Forged pistons are made by compressing a piece of metal into a mold, which aligns the grain structure for increased strength and durability. 
  • Pros: Offers the lightweight benefits of aluminum with greater strength and fatigue resistance, making it popular for high-performance applications. 
• Forged steel: Used for extremely high-stress, heavy-duty applications due to its exceptional strength and durability. 

This video explains the difference between cast, hypereutectic, and forged pistons: 51sFirst Place Auto PartsYouTube · Aug 9, 2022