Subaru 2.5L DOHC FB25 Excessive Oil Consumption

Most Subaru owners are well aware of the oil consumption problems these engine develop. The EJ25 timing belt engines had this issue but not as bad as the new FB25 engines that run the 0W20 engine oil. The EJ25’s mainly had head gasket issues and oil consumption will not get excessive till well over 100k, especially if maintained correctly. Most of the rotational drag is at the piston rings to cylinder wall contact. Even something as simple as a smaller oil pump will effect fuel economy.  The 0W20 oil is almost like water and theses engines had a warranty lawsuit where SOA (Subaru Of America) was replacing them under warranty. This particular vehicle passed ownership and was driven beyond the warranty range so the customer got stuck with the bill. We replaced the short block but did some investigation as to why it was burning so much oil. The bottom rings of the pistons are stuck and drain back holes plugged up, this is the same as the EJ25’s except the piston rings are a lot thinner and oil viscosity very low so it burns a lot easier and the problem develops before the engine even reaches 100,000 miles. Take a look at the picture below to see the stuck bottom piston rings.


Cylinder #4 Piston Picture Stuck Rings

This engine burned oil so badly that it damaged the catalytic converter and completely burned up the exhaust valves. It uses puck shims for valve lash so you have to replace the valves at there original installed height or do some math and purchase different thickness valve shims to get the correct valve lash. We have a valve re-face machine to do this or just have the machine shop set them up for you. The engine does not have a timing belt anymore either but even at 150k all the timing chain components are okay. It’s amazing how clean these engines are on the inside from requiring to use synthetic oil. literally no bearing wear and the chains, tensioners and guides were in perfect condition, the engine was just an oil burner.

Being an independent repair facility these engines are pretty new to us. We are still seeing that most of our common repaired vehicles to be 10 years or older. With the Subaru’s most of our work is still on the EJ2.5L and EJ2.0L engines. I’m curious to hear any feedback from our readers as to what experience, repair tips and/or advice or even common failures that your seeing. Please comment below, follow the post and/or email to get question responses from me. Thank you for reading, happy wrenching :-).


Question: Why do you think that most automobile manufacturers are changing from timing belt engines to timing chain engines? It’s not like it’s a new technology, the first overhead cam engines were timing chain from my experience.


This post was written by: Martin Hand


If you find this information helpful please consider a donation. These articles, questions and comments are very time consuming so even a small donation gives me motivation to keep educating automotive owners. Donations will allow us to continue open questioning/comments, automotive education and repair tutorials in the future as the business grows. All proceeds go to the expansion and maintenance Thank You

Martin Hand

About Martin Hand

ASE Certified L1 Advanced Mastertech. Martin Hand has over 15 years experience in Asian and European Import Auto Repair. Specializing in electrical diagnosis, engine performance, AT/MT transmission repair/rebuild. Martin is also pursuing a degree in Computers Science & Information Systems starting at Portland Community College while he plans to transfer to OIT. Certified in Java application level programming, experienced with other languages such as PHP, Ruby, JavaScript and Swift. Martin has future plans of automotive diagnostic software development.


  • Lonnie Lockhart says:

    Hi Martin – this is very impressive. I am wondering if you know if Subaru has improved their engine design on the new 2.5 engine that they are using in the 2019 Forester? I think I read something that you may have written titled “Why has Subaru Quality gone downhill” – but I can’t seem to find it on the internet. Sure wish I lived closer to your shop (I live in Utah – do you know any good mechanics shop that you would recommend here?) Thanks, Lonnie Lockhart

    • Martin Hand Martin Hand says:

      Sorry, I do not know a repair facility that I could refer you to in Utah. I believe Subaru has corrected the problem with the new Foresters and all FB25 engines. Thanks for reading…

Leave a Reply

Your email address will not be published. Required fields are marked *