Subaru 2.5 Change Interval

Joined
Oct 8, 2017
Messages
1,261
Location
USA
2017 Subaru with the 2.5 naturally aspirated. Why did the oil change interval dip to 6k on these? The older Foresters were 7.5k, if I remember correctly. If I'm running Valvoline synthetic, can I run it past 6k? 4k of the miles are highway 75+mph in July road trip. I ran 5w30 because I knew it would be working hard. I picked up some NAPA today on sale, but am contemplating running 1-1.5k more instead of changing.

Opinions? Ideas? Past 60k miles, so no more engine warranty.
 
I'd guess that Subaru lowered the oil change interval due to fuel dilution related to direct injection. Check the oil level - has it gone up? Does it smell like gas? If so, I'd change it.
 
M1 5w30 EP or vanilla with factory filter, can't go wrong with these going forward. And good price at WM.
 
I would worry more about the coolant health than the oil TBH. But keep in mind, the recommended OCI is based on synthetic AFAIK; if they are saying scale it back, at least do a (they are so cheap now) OA before you decide to go against their recommendations.

I did a pre-purchase inspection on a 2017 Crosstrek a few weeks ago. It failed within 2.5 minutes. 70k mi off-lease vehicle being sold by local Dealership. Casual glance was OK. Opening the hood and the inspection was over in 30 seconds. All non-painted surfaces (machined pulley faces, galvanized hose and wiring clips, etc. were rusting. Radiator bolts had substantial rusting starting to bubble up through the paint. I did not charge for the inspection because they came to me. 2.5 minutes of my time isn't worth charging for.. ;)

The electrolysis/grounding issues with these engines is just not at all fixed as the company likes to say (e.g., the cause of all the historical hg failures). Keep an eagle eye on coolant health and electrical health. Even new ones can go bad. I don't hate Subaru and have met many I really like. But they have some design issues they keep NOT working out.

I wish I had taken pictures of it but at the time I didn't have my phone on me.
 
Why did the oil change interval dip to 6k on these?
Because folks from past 'generation' (2011-2016 IIRC) were complaining that their vehicles are oil burners. Subaru says a quart of oil loss per OC interval is OK but folks were not buying it. So they lowered OC interval for newer vehicles.


Keep an eagle eye on coolant health and electrical health.
How does one do that? I would just replace the coolant every 5 or 6 years even though Subaru says 10 years.
How do I check electrical health? I am asking because I started noticing rust spots on my 6 YO Forester. I admit I don't wash the engine bay. I don't even clean it other than blowing air every time I go to the carwash. Non-painted surfaces like pulleys are rusting and the dealership says there is nothing one can do about it. We live in a rust belt (northeast). TBH, I am sick of hearing this, but I don't know what I can do to prevent it.
 
It is not about oil consumption, it is so they can do six oil changes during the 36,000 mile bumper to bumper warranty and ten times during the 60,000 powertrain warranty. In Europe the service interval for the same car is every 12 months or 15,000 kilometers. There is a 2015 Crostrek owner who reached one million miles this week and he changes the oil once every 12,000 miles with 0W20 synthetic.
 
If you want to reduce electrolysis that an owner can do, you can improve the ground of each cylinder head to the chassis. A separate ground strap for each cylinder head. Check the condition of existing ground straps but you can add additional aftermarket straps. Galvanic corrosion caused by direct contact between dissimilar metals, cannot be eliminated.

if you want to check for coolant electrical health with the engine running is you can use a multimeter and dip the positive lead into the coolant, negative to the negative terminal of the car battery. The rule of thumb is greater than 0.4 volts means coolant needs replacing.
 
2017 Subaru with the 2.5 naturally aspirated. Why did the oil change interval dip to 6k on these? The older Foresters were 7.5k, if I remember correctly. If I'm running Valvoline synthetic, can I run it past 6k? 4k of the miles are highway 75+mph in July road trip. I ran 5w30 because I knew it would be working hard. I picked up some NAPA today on sale, but am contemplating running 1-1.5k more instead of changing.

Opinions? Ideas? Past 60k miles, so no more engine warranty.
 
I have a 2018 Subaru Forested Premium 2.5, and change the oil every April and October regardless of mileage. I use 0w20 as recommended by Subaru, and only put 3k miles on it every 6 months . Don't over think it.
 
Last edited:
Because folks from past 'generation' (2011-2016 IIRC) were complaining that their vehicles are oil burners. Subaru says a quart of oil loss per OC interval is OK but folks were not buying it. So they lowered OC interval for newer vehicles.

I don't believe this was a situation of consumer "complaining." There were serious issues with a unacceptable percentage of engines burning a lot more than a quart per recommended OCI. Subaru replaced an unprecedented number of 2.5 engines over a 4 year span. I came a cross a lot of this while researching my 17 3.6 purchase.
 
I've been also wondering about the same question for the past 5 years with my '15 Subaru. AFAIK, there is not an official answer for the switch to 6k, but it is probably a combination of one or many of the answers given above.
I try to stretch mine out to 7k with store brand 0w20, but l check the oil level periodically. Thankfully, my current Subaru does not consume oil, but my previous one did.
 
2017 Subaru with the 2.5 naturally aspirated. Why did the oil change interval dip to 6k on these? The older Foresters were 7.5k, if I remember correctly. If I'm running Valvoline synthetic, can I run it past 6k? 4k of the miles are highway 75+mph in July road trip. I ran 5w30 because I knew it would be working hard. I picked up some NAPA today on sale, but am contemplating running 1-1.5k more instead of changing.

Opinions? Ideas? Past 60k miles, so no more engine warranty.
I performed two used oil analysis on our subaru - using two different tiers of oil - in an effort to extend the OCI to 9K miles.

The Wagon is driven about 25k miles a year, and that is about 70% highway. with a full 50 min warm-up commute.

The UOA are in the UOA section, somewhere.

They (UOA) showed MUCH LOWER than average wear metals for that engine, and the oil was just ripe for a change at 9K.

There is your objective data. The engine runs better than ever with almost 80K on it,

-Ken
 
They dropped the interval to 6000 because people kept running the engine dry on 7500 intervals. The early FB25 engines had oil consumption. There have been a few UOAs on here and the FB25 seems to do well on 7500 - 10K intervals. I am still under the 5/60 powertrain warranty, but I have no oil consumption so I may just extend to yearly intervals like I did with my Focus. I see no reason to change at 6K intervals since this engine isn't an oil burner and I won't have a need to warranty the thing.

I'd guess that Subaru lowered the oil change interval due to fuel dilution related to direct injection. Check the oil level - has it gone up? Does it smell like gas? If so, I'd change it.

This is a port injected engine still.
 
2017 Subaru with the 2.5 naturally aspirated. Why did the oil change interval dip to 6k on these?

Based on my experiences having owned two vehicles with this engine and running a website where literally thousands of owners of vehicles with this engine have reported their findings, I am of the opinion that the limitations of Subaru's OEM oil filter is why the recommended oil change interval was lowered from 7500 miles to 6000 miles.

That being said my current 2018 Outback 2.5L started noticably consuming more oil during each interval AFTER the 60,000 mile mark. By 90,000 miles it was consuming a quart of oil every 6000 miles using RGT 0W20. I am at 111,000 miles now and it has consumed a half quart of Mobil 1 0w20 EP after 6000 miles.
 
I'd guess that Subaru lowered the oil change interval due to fuel dilution related to direct injection. Check the oil level - has it gone up? Does it smell like gas? If so, I'd change it.
I don't think the 17 is DI. I have an 18 and nowhere can I find that it is DI however my 2019 Impreza 2.0 is DI.
 
^^ this. We have a 2017 OB 2.5 and it is not DI, yet still 6k OCI per Subaru. Haven't extended yet, as we're just under the 36k warranty, and haven't yet done an oil analysis, but it uses no discernible amount of oil by 6k.
As an aside, we have two small 4 cyl Hondas, one is port FI (with 100k miles) and the other is DI (with 23k miles). At 3k miles on the oil, the older engine's oil still looks like dark honey, the DI oil is very black and sooty looking, yet the Honda OCI is around 10k.
 
Last edited:
I performed two used oil analysis on our subaru - using two different tiers of oil - in an effort to extend the OCI to 9K miles.

The Wagon is driven about 25k miles a year, and that is about 70% highway. with a full 50 min warm-up commute.

The UOA are in the UOA section, somewhere.

They (UOA) showed MUCH LOWER than average wear metals for that engine, and the oil was just ripe for a change at 9K.

There is your objective data. The engine runs better than ever with almost 80K on it,

-Ken

Good info. Put 200k on a 2005 Forester before this one. 7000-7500 on conventional/synblend mostly. Some syn here and there when it was $15 or less for 5qts. Pretty certain it's not DI so none of those issues. Was curious what made this engine, with synthetic required, worse LOL

It uses a bit of oil...added a full quart in the first 4k after pulling 80+mph into 20-40mph headwinds for a 1200 mile day across the Midwest in July in 90+ temps. 4k-6k no loss on dipstick. Last 6k interval it used about 0.25-0.5 quarts with the typical 35 miles to work, 35 miles back, 95% highway.

The other piece is, the weather is nice next week and who knows when the rainy season will hit LOL
 
I don't believe this was a situation of consumer "complaining." There were serious issues with a unacceptable percentage of engines burning a lot more than a quart per recommended OCI. Subaru replaced an unprecedented number of 2.5 engines over a 4 year span. I came a cross a lot of this while researching my 17 3.6 purchase.
The OP's engine is FB25. I have not come across any thread on Forester boards where a 2.5liter engine was replaced for oil consumption. But a few complaints that the engine 'drink's oil, and they got above answer from the SOA. 3.6 outback engines, possible but I don't frequent Outback forums.

I got the above info from Forester boards. I personally do not have any experience with oil consumption.
(I can't figure out who posted this comment. If you did, your quote tag was misplaced, hence tagged you. Ignore that part if you didn't comment.)
 
Back
Top