Subaru Boxer Engine

EVERY Subaru runs with the Subaru Boxer Engine; named for the horizontal movement of the pistons - much like boxers throwing punches. On this page you will learn why Subaru chose the Boxer engine, how it works, and the safety, performance and handling advantages it brings to the driving experience.

This page contains information explaining:
  • What is a SUBARU BOXER engine
  • How Subaru's Boxer engine works
  • Performance, Safety, and Handling Advantages of a Subaru Boxer engine
  • Why Subaru's BOXER engine is better than competitors.
Let's start with this video explaining How Subaru BOXER engines work vs other engines

Drawn from a century of intelligent performance, the horizontal layout of the SUBARU BOXER® engine combines balance with power and efficiency. You'll find one at the heart of every Subaru model.


Find out how the SUBARU BOXER® engine offers a host of advantages over competitive designs.

There are different SUBARU BOXER® engines for the different styles of Subaru vehicles, tailored to the vehicle and meeting the performance requirements of customers' needs. But every engine is built from the same simple, efficient design.

Why The SUBARU BOXER® Engine?

The engine is called a 'Boxer' because of the movement of the engine's pistons resembling the movement of a boxer's fists in the horizontal plane. However, unlike the boxer's fists that both move in the same direction, half of the 'Boxer' engine's pistons move in the opposite direction. This very important difference provides the key benefits of the horizontally-opposed (Boxer) engine layout where half of the total number of cylinders and therefore pistons lay on their sides in an east-west configuration moving in opposite directions. 

Contribution to Vehicle Handling and Stability

The key benefit of the Subaru 'Boxer' engine's horizontally-opposed layout is not about its power output or environmental performance but its contribution to the vehicle's handling, stability and as a result, safety.

Firstly, because the cylinders in the Boxer engine lay on their sides the overall height of the engine is significantly lower especially when compared to the more normal 'inline' engine where all the pistons move in the same direction in a north-south configuration. This results in a low center of gravity that has very significant advantages in terms of the vehicle's handling and stability, by helping to keep the tires more firmly planted on the road surface as a result of a lower level of weight transfer from the inside wheel to the outside wheel when cornering. 

Furthermore, because half of the total number of cylinders is on one side and the other half on the opposite side with a common crankshaft sandwiched in the middle the left-right weight distribution with the engine positioned on the center line of the vehicle is equal. This also makes a very significant contribution to vehicle balance, stability and handling particularly when cornering or making rapid changes of direction.

Durability, Reliability and Lightweight

As mentioned previously because the cylinders lay on their sides positioned in opposite directions with a common crankshaft, the size and therefore the weight of the Boxer engine is relatively lightweight. Subaru 'Boxer' engines also feature all aluminium construction of the crankcase and cylinder heads that also significantly contributes to weight reduction. This not only improves the power to weight ratio and therefore driving and environmental performance but also again helps handling and stability.

Because the pistons move in opposite directions the natural rotational balance of the engine is very good due to the cancellation of the piston inertia forces that move in opposite directions. This means two things;

Good rotational balance means lower levels of vibration and harshness, which translates into less wear and tear and therefore higher levels of durability meaning a more reliable and lower cost of ownership.
Because the crankshaft is sandwiched between two very rigid crankcase halves it is very well supported and therefore its durability is significantly enhanced and because it absorbs less vibration its design can be of a much lighter construction. This not only contributes to the over lightness of the engine but also means a freer revving more responsive engine, both attributes bringing improvements in vehicle active safety through improved driveability.

Crash Safety Contribution

Another key benefit of the Subaru Boxer engine design is that it could save your life! This is the result of its low height when positioned in the front engine bay. In a full frontal or even an offset accident a severe impact will cause the front of the vehicle to crumple and subsequently cause the engine to be driven backwards towards the passenger compartment with potential penetration and severe trauma to the front occupants. Due to its low height, the 'Boxer' engine can be redirected under the floor of the passenger compartment avoiding any penetration of the passenger compartment and therefore reducing the chance of front occupant injury.

Some information on the Subaru Boxer Engine taken from: //

Ed Reilly Subaru

150 Manchester St
Directions Concord, NH 03301

  • Sales: (603) 225-0200
  • Service: (603) 225-0200
  • Parts: (603) 225-0200

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  • Flat layout allows engine output to flow directly into the transmission. This linear flow of power reduces engine components and inefficiencies, resulting in better fuel economy. Subarus are the most fuel efficient AWD vehicles in America, often getting better gas mileage than its FWD competitors.

  • By lowering the center of gravity of the engine, you also lower the center of gravity of the entire vehicle. A lower center of gravity = more responsive - particularly when cornering or doing evasive maneuvers.
  • Less vibration. The natural counter punch of the opposite piston cancels out unwanted vibration where inline and v-type engines require additional components to accomplish this.

  • Safety. In the event of a frontal accident, the boxer engine's low center of gravity allows the engine to drop "below" the passenger compartment instead of in it.
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