Subaru 2.5L (150 cu in) firing order — diagram & guide

As a brand, Subaru has always been known for its unique boxer engines, and the 2.5-liter is the most popular among enthusiasts. If you own a car with one of these, it’s important to check the oil level and spark plugs regularly, and the Subaru 2.5L (150 cu in) firing order helps with that.

So, we’ll help you with our guide on the firing sequence and cylinder configuration to set you on the right track when it comes to engine maintenance.

Subaru 2.5L firing order

Before we get into any details, it’s crucial to state that the Subaru 2.5L firing order is 1-3-2-4 which is a unique firing pattern for this engine. Other four-cylinder engines usually have a firing order of 1-3-4-2, so this one is pretty specific.

However, that’s not the only specific thing about this engine since the cylinder configuration is also unique to this engine. Instead of the straight-four layout, this engine is a “boxer” four-cylinder powertrain. It means the cylinder pistons are moving towards each other.

We’ll also discuss the cylinder configuration in the next section so you can have an easier time identifying the cylinders.

Subaru 2.5L cylinder diagram

The next step is a crucial one for using the 2.5-liter firing order and that’s figuring out the cylinder configuration. As a boxer engine, the Subaru 2.5L has cylinders 1 and 3 on the passenger’s side and cylinders 2 and 4 on the opposite side.

So, the first cylinder is the closest one to the pulley on the passenger’s side of the engine. The difference between this engine compared to the straight-four engine is that the cylinder pistons of this one go toward one another in a combustion cycle

Cylinders 1 and 2 fire in the boxer sequence as well as cylinders 3 and 4 in pairs, so now you’ll know how to identify each cylinder.

Subaru 2.5L vehicle applications

Now that we’ve gone through the important specs of the engine and its firing order, the next step is to discuss the list of the vehicles powered by it. This way you can see if the firing order is fitting for your engine:

• Subaru Impreza WRX
• Subaru Impreza WRX STI
• Subaru Forester STI
• Subaru Legacy
• Subaru Outback
• Subaru Forester XT

Whether it’s a turbocharged version of the engine or a regular one, the firing order 1-3-2-4 is fitting for all these models.

Our take

Overall, the 2.5-liter Subaru engine proved to be pretty reliable, and using the Subaru 2.5L firing order is hopefully now at least a bit easier for you. The key point here is to understand the unique boxer engine configuration and cylinder numbering, so our team is happy to have helped clear that up.