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Everything you need to know about Subarus 2.5 engine


Subaru models

When you buy a car, you know that the engine is the heart of the machine. But what are the details behind the Subaru 2.5 engine? By having a better understanding of what’s under the hood of your vehicle, you’ll have a better idea of ​​what your vehicle can do for you.

What are the characteristics of a Subaru 2.5 engine?

The Subaru 2.5 engine is a naturally aspirated turbocharged 16-valve four-cylinder engine with a displacement of 2,457 L. Depending on the year, make, and model in which it appears, the engine power varies from 155 to 172.6 and from 140 at 170 lb-ft

But what is going on with this engine beyond the specifications? What kinds of questions do owners have? We’ve compiled information from all over the internet, including the NHTSA website and extensive vehicle history database, so you can find everything you need to know right here, in one place.

History of the Subaru 2.5 engine

The Subaru 2.5 engine, which comprises a range of different engines known as Subaru’s EJ25 series, the EJ25D, EJ251, EJ252, EJ253, EJ254, EJ255, EJ257, and EJ259, was introduced in various versions of the Legacy from 1994 to 1996, including the legacy GT, LSi, and Afuera.

In developing the Subaru 2.5 engine, the manufacturer moved away from the typical inline-four or V-four engines for a four-course design, which Subaru refers to as a “boxer” engine. It’s called that because the pistons are 180 degrees apart, so they push toward each other, like hitting boxers.

This unique approach to engine design offers several advantages. The flat design allows direct engine and transmission input, improving fuel efficiency, while the reduced vibration caused by opposing pistons reduces the need for additional components found on many basic V engines to compensate for this.

The lower center of gravity provides better performance and handling. This same feature allows the engine to drop below the passenger compartment in the event of an accident instead of inside the passenger compartment, reducing injuries.

Over time, the EJ25D was replaced by the EJ254 and EJ257, which are DOHC models, which were used in limited numbers due to the complex four-plane architecture that made it difficult to change plugs. Subaru solved the problem by using long-life platinum spark plugs for less frequent maintenance.

Due to the architecture, many other Subarus received the single overhead camshaft configuration, starting with the EJ251. The EJ252 was designed specifically for California emissions laws, while the EJ253 reduced its horsepower by 5 HP and replaced a MAP sensor with an MAF sensor.

What models have a Subaru 2.5 engine?

There are several Subaru models that have a 2.5 engine. The start of the 2.5 engine was the Legacy, including the EJ25D from 1994-1999, the EJ251 from 1999-2004, the EJ252 from 2000-2002, the EJ253 from 2009-2012, the EJ255 from 2005-2012, the EJ257 from 2005- 2006 and EJ259 of 2004.

The Outback also saw several of these engines, starting with the 1996-1999 EJ25D, 2000-2004 EJ251, 2000-2002 EJ252, 2003-20012 EJ253, and 2005-2020 EJ255. The Baja used the EJ251 from 2003 to 2005 and the EJ253 from 2005, the Baja Turbo used the EJ255 from 2004 to 2006.

The Forester used the EJ25D from 1997 to 1998, then switched to the EJ251 from 1999 to 2004, to the EJ253 in 1999 and again from 2005 to 2010, to the EJ254 from 1998 to 2002 in T25 version and from 2004 to 2020, to the EJ255 from 2004- 2013 and EJ257 from 2004-2005 in the XT version.

The Impreza only used the EJ25D engine for one year, in 1998, then switched to the EJ251 from 1998 to 2003, to the EJ253 from 1999 and again from 2004 to 2011, to the EJ255 from 2006 to 2014, and finally to the EJ2057 from 2004 to 2018.

People also ask

Are Subaru 2.5 engines reliable?

Although Subarus is known for its reliability, its 2.5L engine has some issues. shared with the 2.0 engine. You tend to have head gasket problems and crankshaft oil/seal oil leaks, as well as a knocking noise from the fourth cylinder, which runs the hottest and cools the least of all the cylinders in the engine.

What is the Subaru 2.5 I engine?

The Subaru 2.5 engine is a boxer engine, meaning that instead of the pistons moving in and out at an angle, the pistons move 180 degrees, like boxers throwing punches at each other. This creates a smoother ride and better handling when the vehicle is moving.

What are the specifications of the Subaru 2.5 engine?

The Subaru 2.5 engine features a bore of 99.5 mm and a stroke of 79 mm. The 1996 engine has a compression ratio of 9.5, which was updated to 9.7 from 1997 to 1999 and finally to 10.0 starting in 2000. It is capable of delivering between 155 and 170 HP and 140 and 176 lb-ft. of torque

How long do Subaru 2.5 engines last?

Many owner reviews mention that the Subaru 2.5 engine provides many years and miles of reliable service. These include over ten years of reliable service and over 200,000 miles without serious vehicle problems.

Are Subaru 2.5 engines interference engines?

All Subaru 2.5 engines are interference engines, but what does that mean? An interference engine provides more power with better fuel economy because the pistons and valves can interfere with each other during operation if a specific timing is not maintained. If the timing belt breaks, it can cause serious damage.

Buy a used car? Make sure you do it safely

Start by reviewing your vehicle’s history! We’ve partnered with brands and websites like KBB, NHTSA, and more to give you a free tool to use on the go, so you can make a smart decision quickly.


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