Any reason NOT to run 15K OCI with M1EP on a Subaru NA 2.5 boxer (80% highway) ?

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UOA has its benefits, one is basically useless, you need a trend to really see if the oil is holding up so, IMP, don't bother with a UOA, if you want one do it at the one year or 15,000 mark and see what it looks like. One OCi at 15,000 is not going to hurt anything if the UOA is not looking good.
 
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Using M1EP 0w-20 with Fram Ultra. The 12K warranty on a short block replacement is up. So far the oil consumption is around 1/4 qt in 7500 miles. We take weekly of highway trips of 30-250 miles so I doubt that fuel dilution is an issue. Not a GDI engine.

Mobil claims 15K (old) and 20K(new) between oil changes with M1EP.

Given this usage, is there any real reason not to go with 15K OCI's?
Don’t go by feeling and what internet hacks tell you, lol. Do a couple of UOA’s to put your mind at ease.
 
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With that said, the only time my FB25 consumed oil was on Mobil1 AFE. It went through 1/2 quart or so during the 6000 mile change interval. Every other oil change on other oil it's never needed a drop over the 6000 (or sometimes more ...) interval.

My Subaru engines have had the worst oil consumption using M1 AFE 0w20 as well, M1 EP 0w20 is better but not able to push it much beyond 6000 miles before the low oil light comes on. To date I have probably had the best results with Valvoline 0w20 oils to include Modern Engine and Full Synthetic Maxlife.
 
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Ahhj back to the Blackstone UOA! Why would you pay for this? Their cheapest analysis is $30. Just change the oil. Never understood why anyone takes the times to produce a sample and send it off for analysis. For the less than the cost of the analysis I can change the oil and filter .

Some you would rather spend a dime to save a nickel.
I'm with you, change it Oil Cheap, Engines expensive.
 
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Using M1EP 0w-20 with Fram Ultra. The 12K warranty on a short block replacement is up. So far the oil consumption is around 1/4 qt in 7500 miles. We take weekly of highway trips of 30-250 miles so I doubt that fuel dilution is an issue. Not a GDI engine.

Mobil claims 15K (old) and 20K(new) between oil changes with M1EP.

Given this usage, is there any real reason not to go with 15K OCI's?
Yes.
 

Rex

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Nope! I have a 2011 Outback and run it 10-15K between oil changes. 224,000 miles on it and runs strong.. - Amsoil
 
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My Subaru engines have had the worst oil consumption using M1 AFE 0w20 as well, M1 EP 0w20 is better but not able to push it much beyond 6000 miles before the low oil light comes on. To date I have probably had the best results with Valvoline 0w20 oils to include Modern Engine and Full Synthetic Maxlife.
I guess I would have to have major consumption to know if I was having issues. I just started to get 6k miles in 6 months in my 18 Legacy. Previously it was more like 2 - 3k miles every 6 months if that. My first and I think second change in that was AFE. Since then it has been EP. My 19 Impreza has the same issue. My last OCI was just around 3k and I was lucky due to having a few gigs and driving to DC twice otherwise it would have been less than 2k.. Prior that that my last was around 1,325 miles, 1,653 before that and about 4476 on my first OCI. I'm just starting to really drive again so I should be closer to normal mileage again unless we lock down again.
 
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I have no idea why you would want to push an engine known for consumption/drama any further than what they call for. 5K miles man, it's simple and cheap.
I guess my question is why? Oil is cheap and plentiful. Engines are not. Why push the threshold? Just to brag to other people you can go 15k on oil? If someone told me that, I honestly wouldn’t care. I’d say cool and go on about my life.
 

NO2

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I was of that philosophy, but I did a UOA to see how shot the oil was, then I extended the OCI by 50%
for the rest of the vehicle service life That saved me some bucks. The Subaru OCI of 6K miles was very conservative givin our use of this vehicle, running 23K mainly high speed highway miles per year.
What oil were you using? We have a similar usage pattern.
 
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While apples to oranges, I have a 17 Outback 3.6. I've posted a few UOA's showing 10k run where Blackstone says 12k+ is in order. I have settled on M1 EP 5-30 and Fram Ultra 8k. That is my comfort zone. My 3.6 loved Mobil 1 5-30 EP. My engine burns little over that 8k. Why not 10k or 12K? For me, timing chain wear. Not enough info for a non-mechanic like me to make a truly informed decision.

If I with the 2.5 Subaru engine, I'm going with a cheaper oil like ST synthetic 5-20 and quality filter with a 5k run. I see that as the safe zone.

For the post talking down to me as a UOA guy....you are certainly correct that you could change oil instead of buying a UOA. But I get a utility out of them and I enjoy the reports. Under a relatively same premise, I could pick apart whatever vehicle you are driving and show you that you could have picked a more economical choice.
 
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Yes I have completed three oil changes on the 2021 Outback 2.5L with the most recent one being yesterday for the 18000 mile interval. I have been using up my stash of Valvoline Modern Engine 0w20 and Wix 57055 filters. No problems to date.

I find it amazing that for all the complaining and worry I hear about head gaskets and other potential issues with this engine design you say you have no issue with yours, while claiming it is inherently problematic, and essentially claim that extending an OCI will not contribute to anything considered problematic. It just seems to be a bit inconsistent.
The issues are all design and materials, where the oil used is largely irrelevant. I feel on the older EJ253, that engine wasn't well suited to a conventional 5W30 under stress. The owners manual table in those allowed 20W50 where appropriate.

I have no fear of Subaru HG issue with anything made since the early 2000's. I think others might bring that up.

To sum up shared observations, would you say if my engine is currently extremely noisy, that it is currently defective?

I was going to put the Subaru genuine and the blue Fram-a-roo filter on it and head to the dealer
with a warranty complaint. Do you run premium given the incredible 12:1 compression ratio?
 
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