Subaru 2.5i EJ25 Engine: Problems, Longevity, And Specs

Subaru company is well-known for its practical and durable technologies. But are all its engines so good that they can last long and cause no problems? We doubt it. So, we start our series of articles about different Subaru engines with one of the most popular and controversial units ever made by this company.

Today, you will learn more about the Subaru 2.5i boxer engine (EJ25) that is considered to be durable and powerful but still problematic and with a lot of surprises. We are going to tell you about its main features, durability, and common problems, and also about our points of view on whether you should buy a vehicle powered by this engine or not.

Key features and my opinion about the engine

• Production years:1994-2024
• Average lifespan of EJ25:150,000-190,000 miles
• Fuel supply type:port injection
• Power range:155-310 hp
• Fuel efficiency:average
• Engine block material:aluminum
• Engine reliability score:medium
• The most common problems:extremely afraid of overheating, oil consumption, numerous leaks.

What's the Subaru 2.5-liter boxer engine like?

Today, we are talking exclusively about the EJ engine with 2.5 liters of displacement and it's the biggest engine in the series. The four-cylinder engine is known to be one of the best in the series, too.

Well, we perfectly know that Subaru cars are pretty much always associated with boxer engines. And the 2.5-liter one is the brightest representative in this series. The boxer engine means that the cylinders are located not in a row like in an in-line engine, but opposite each other. That's why, sometimes, these engines are also called the opposite units.

Here are some things you should know about the 2.5i engine offered by Subaru:

• the boxer design has its pros and cons, and this is a big reason for arguments among automotive experts and Subaru fans;
• these engines are OK in terms of all important features, but they are slightly more complicated in terms of maintenance and repair;
• the 2.5-liter engines in Subaru cars can be turbocharged and have up to 320 hp of power, but we are talking about naturally aspirated ones (160 hp and more);
• these engines were first introduced in 1995 and they are still made and offered in some Subaru models;
• if you investigate the market of used Subaru cars, you will see that this engine can be found in almost all popular vehicles offered by the brand;
• the possibilities of tuning for these engines are just unbelievable, so you can buy it and make it much more powerful if you like upgrading things.

There are still some flaws in the boxer engine design. And they will influence what you think about the Subaru 2.5i engine. We will talk about these problems later, in a special section.

So, now you know a little more about the 2.5-liter 4-cylinder engine in Subaru cars. You shouldn't think this engine has always been the same. It had a lot of small and major changes and modifications, especially for fitting it into certain ecology categories and requirements.

What are the maintenance and repair problems of the Subaru 2.5i?

This engine is a boxer engine, so it has a special construction that needs certain experience and knowledge from a car mechanic. If you've never dealt with boxer engines, you will not be able to maintain and repair this engine at all.

So, finding a good mechanic is hard and you will probably need to visit a Subaru dealer even for minor repairs. This will result in high expenses which may be a problem in the long run.

Here are some examples of what we are talking about:

• changing or even checking spark plugs and coils is a disaster and you will have to take apart half of your vehicle's engine compartment;
• if something needs to be done with the engine head or any other part, you will have to take the engine off first;
• parts will be a problem, especially if you want to spare some money and buy aftermarket parts for the 2.5-liter engine;
• the overall price of maintenance and repair is much higher than that of an in-line engine with the same specs.

But boxers are more powerful than the in-line engine. They also provide a lower center of gravity, so they will obviously make your Subaru more stable on the road and easier to steer at high speed than any other competitive vehicle.

What about the longevity of the Subaru 2.5i engine?

The longevity of the engine is just average for this class of units. You will be able to drive your Subaru equipped with the 2.5-liter boxer engine for about 200,000 miles which takes approximately 7 to 12 years depending on your yearly mileage. This is not a lot, but it's not bad, too.

We know for sure that the 2.5-liter boxer engine by Subaru will be a good option in terms of longevity if maintained and repaired properly. Once you forget to change the oil or filters or you neglect some obvious signs of problems, this engine turns into a big disaster instead of being a very durable unit.

We've seen some Foresters with 250,000 plus miles on their odometers. But the condition of the engines at this mileage wasn't good. It could consume some oil, vibrate, lose power, etc. So, we believe, at 200,000 miles, the 2.5i engine will need a thorough repair with changing of pistons and piston rings, investigation of the cylinders' condition, valve seals replacement, etc.

What are the common problems with the 2.5i Subaru engine?

Unfortunately, some of the common problems may happen way before the engine is thought to retire. Some problems may be fatal and they may happen as early as 100,000 miles or even before that mileage.

Here are some of the most problematic parts of this engine that are considered to be common issues and cause premature death of the Subaru engine:

1. Head gasket. The problem with the head gasket can kill the engine very fast. And the position of the head gaskets in this engine means they will be problematic - they are under constant pressure. Replacing them is a hard and expensive task because of the boxer construction.
2. Loss of power. There are dozens of reasons why your 2.5i engine may just lose power and become sluggish. But to solve this problem, you will need to invest a lot of time and money in research.
3. Oil consumption. Reports say that the 2.5i engine starts consuming some oil as soon as 100,000 miles. But over time, the consumption goes up, and sometimes it may even lead to low oil levels and other problems that come after that.
4. Poor oiling. Some 2.5i engines are known to have poor oiling of some parts because of very thin oil channels. Over time, these channels get clogged with bad oil and deposits and become inefficient in supplying some parts of the engine with the proper amount of oil.

Repairing this engine is not cheap at all. And the price of maintenance and repair may be one of the most important issues for the owner.

We believe that your Subaru 2.5i EJ25 is not a bad option, but it should be repaired and maintained without any hesitations in a very good repair shop or better in a dealer's shop. Of course, this will take more money from your pocket, but otherwise, the engine will die soon.

Many Subaru drivers may take normal work of their vehicles for problems. A lot of readers asked me if the "2 Hours from ignition On" a serious warning and I've written an article to explain this - read it if you own a Subaru vehicle.

Should you buy a 2.5i Subaru?

When we are talking about used Subaru cars, you should check whether the year you are looking at is not problematic. If it is, better refuse from buying this vehicle and look for another one. The 2.5-liter Subaru boxer engine may be both, a good investment for a lot of years to come, or just a disaster for your budget.

Check the vehicle, ensure it has been maintained well by previous owners, and check the mileage. If the car has already got over 150K of miles on it, there is nothing that can make you buy this vehicle but a very good price.

If the reason for our discussion is a new Subaru car, we would obviously recommend the vehicle with the 2.5i boxer engine inside. This is a decent and reliable engine that is not going to let you down if you just maintain it according to the requirements of Subaru. But you should know that after 150,000 miles, this engine will become a big problem for your budget asking for one repair after another.

Final words

Our team loves Subaru cars. We don't have it on our fleet, but we've driven a lot of Subarus powered with the 2.5-liter boxer engine. We've also spoken to mechanics, dealers, and some owners of these cars to provide you with the most relevant and up-to-date information on the 2.5i engine.

And in the conclusion, we can say that we recommend this engine new and low-mileage used. If you are buying a high-mileage Subaru powered by a 2.5-liter engine, you should understand that it comes with a big bunch of possible issues that are hard and expensive to resolve.