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That is what I tried later on the usual spots it was present. Not easy to reproduce. I am going to test LSPI theory, as my oil change is only 200 miles away. Will use SN Plus certified oil (Valvoline 0w20) to see it makes any difference.
Okay, just letting you know, I don’t know anything will change. But let us know!
 

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Changed oil to Valvoline Advanced Full Synthetic SAE 0W-20 Motor Oil with API SP rating (exceeds SN, SN Plus). As usual with Valvoline - engine makes less noise overall. So far I had 90 miles round trip with plenty of opportunities to test knocking - nothing, not even a single knock. I tried to maintain speed, slight decelerate/accelerate - just purring @ 1000-1200 RPM while climbing moderate uphills @ 40-45 MPH. The oil temperature was within 188-194 F range. Will continue my journey with SN Plus rated oil ...
 

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Changed oil to Valvoline Advanced Full Synthetic SAE 0W-20 Motor Oil with API SP rating. As usual with Valvoline - engine makes less noise overall. So far I had 90 miles trip round trip with plenty of opportunities to test knocking - nothing, not even a single knock. I tried to maintain speed, slight decelerate/accelerate - just purring @ 1000-1200 RPM while climbing moderate uphills @ 40-45 MPH. Will continue my journey with new oil ...
That's interesting... I changed my oil when I had the issue and it was still the same thing. Maybe give it a few more days/miles and it might start acting up again. Keep me posted!
 

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Interesting info from Valvoline document: US_Val_AdvancedFullSyn_MO_EN.pdf - DocuSign CLM

Valvoline Advanced Full Synthetic ILSAC Grades are approved and licensed for the newly adopted API SP classification, protecting GDI (Gasoline Direct Injection) engines from low-speed pre-ignition (LSPI).

So GDI engines are vulnerable to LSPI after all, and this is more likely the issue with new 2.5L CT engine in situations we observed. So API SP rating oil provides LSPI protection for GDI engines. API SN Plus is providing LSPI protection for small turbo engines.
 

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Interesting info from Valvoline document: US_Val_AdvancedFullSyn_MO_EN.pdf - DocuSign CLM

Valvoline Advanced Full Synthetic ILSAC Grades are approved and licensed for the newly adopted API SP classification, protecting GDI (Gasoline Direct Injection) engines from low-speed pre-ignition (LSPI).

So GDI engines are vulnerable to LSPI after all, and this is more likely the issue with new 2.5L CT engine in situations we observed. So API SP rating oil provides LSPI protection for GDI engines. API SN Plus is providing protection for small turbo engines.
Someone who’s more knowledgeable with O I L stuff can chime in but I’m pretty sure most of the newer oils you can buy should have the API SP classification. I know the oil that I use in my vehicle meet the requirements and it still proceeded to make the same sound. It only stopped once I replaced the EGR. If yours stopped after changing your oil, great. However, keep an eye on it because it could just be a placebo affect and it’ll start pinging again.
 

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Subaru OEM oil is SN rated, it has no LSPI protection whatsoever. This is what it had from factory and at first oil change. I also do not recall clearly if previous oil changes made any effect on knocking or make it disappear for a while. It is my pleasure to keep an eye on new SP rated oil. I got used EGR valve from ebay, it cost peanuts. I would not even bother with dealer, just not worse my time. I could change it at will though, if it is an issue. BTW, in my entire life I never had an issue with EGR valves in any vehicle.

Not sure why we need any clarification of the LSPI issue - the industry adopted SN Plus and SP specifications just to deal with this issue alone. It was serious matter for them and manufacturers.

BTW, Subaru could change ECU to avoid it all together, but it will effect efficiency/emission as they need to keep engine at higher RPMs or keep EGR at low level in this situation. Subaru should not sit on this for long as it will be bigger problem when they need to change engines as a result of LSPI. The symptoms are LSPI, what triggers it is another story.
 

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Subaru OEM oil is SN rated, it has no LSPI protection whatsoever. This is what it had from factory and at first oil change. I also do not recall clearly if previous oil changes made any effect on knocking or make it disappear for a while. It is my pleasure to keep an eye on new SP rated oil. I got used EGR valve from ebay, it cost peanuts. I would not even bother with dealer, just not worse my time. I could change it at will though. if this is an issue. BTW, in my entire life I never had an issue with EGR valves in any vehicle.
The dealer uses Castrol oil as the Subaru OEM oil they don’t offer. Not trying to start an oil thread or anything... I know the Subaru OEM oil is Idemitsu, many other Japanese brands use it as well and they also meet the requirements for LSPI.

First off, why would you buy a used EGR valve? Your car is literally brand new - not even a year old yet! And you would consider putting a used EGR in it? ... Secondly, maybe the EGR in your vehicle might be defective, was built incorrectly, stopped working? Things happen so I wouldn’t rule it out. My EGR was faulty but it was still working well enough because it didn’t trip a CEL light in the car.
 

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Idemitsu is SN rated as well. I bought used, because of it is from parts vehicle - those are the best source of good parts always, because of it was great working car before it was destroyed in accident. I have no desire to spent even an hour to explain this to dealer folks who have no clue about this issue. Thanks to you for pushing dealer to resolve your issue. I would say the same about EGR valve change- it may be back to knocking after a few K miles. I did not hear any knocking when it was brand new.
 

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But unfortunately it is SN rated and I have this oil too. The certification label on the container clearly states it: API SN
 

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It is (backward compatible) with SN Plus, but those are for TGDI vehicles operating at low-speeds and high-loads.
SP is for GDI LSPI problems, not TGDI. And apparently SN Plus was not sufficient to address GDI.
Interesting!
 

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At least we should agree that the source of the knocking was LSPI. Quite a few factors can contribute to it. In your case, it is possible EGR valve was out of specs or at high end of threshold. So new one they installed was at the low threshold and it stopped LSPI. Mine EGR maybe not as bad and somewhere in the middle of tolerances, so SP oil may be the only thing I need in my situation, but it is too early to tell in my case.

BTW, this evening I went to shopping with my family and the car had 2 more adults - no knocking so far. Anyway, with new oil - we could barely even hear the engine.
 

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At least we should agree that the source of the knocking was LSPI. Quite a few factors can contribute to it. In your case, it is possible EGR valve was out of specs or at high end of threshold. So new one they installed was at the low threshold and it stopped LSPI. Mine maybe not as bad and somewhere in the middle of tolerances, so SP oil may be the only thing I need in my situation, but it is too early to tell.
I'm 100% sure my vehicle had something that wasn't oil-related as I've changed the oil three times and ended up with the same problem. I hope you don't have to replace anything on your vehicle. Hopefully, it's something as small as your oil not being up to spec. Just keep monitoring it to see if anything changes.
 

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I'm 100% sure my vehicle had something that wasn't oil-related as I've changed the oil three times and ended up with the same problem. I hope you don't have to replace anything on your vehicle. Hopefully, it's something as small as your oil not being up to spec. Just keep monitoring it to see if anything changes.
Whatever it was in your case and other cases described in this thread - it was LSPI. This is what makes knock as fuel ignites too early before piston reaches top point, so it actually tries to push it backward for split second (this is what makes knock), but flywheel and crankshaft momentum overpowers this and then "burning" fuels pushes it forward, as it should. Burning is not a good term though - it is called detonation - very violent event. Imagine the matchstick that instead of burning slowly - it detonates like grenade into smithereens in your hand (engine). The SP rated oil has additives or lacks contributing components to trigger ignition, so it blocks this early ignition, ergo helps to stop it from happening, so no knock. Those measures only help to block LSPI when engine is operating normally. When something is really out of wack - they would not be able to block LSPI from happening. I am thinking, if LSPI is possible even in normal operating conditions, the SP oil may help to resolve issue with normal conditions.

Also, the fact your car has SP rated oil may be a contributing factor for EGR replacement success. So your engine is operating normally now and SP rated oil makes sure LSPI is not occurring while in normal operation.
 

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I just checked my stock of Subaru OEM oil and it has API SN and GF-5 certifications - https://images-na.ssl-images-amazon.com/images/I/917hiDbpfbL._AC_SL1500_.jpg
Same for IDEMITSU ZEPRO 30010095-95300C020 Eco Medalist Advanced Moly 0W-20 Engine Oil - https://images-na.ssl-images-amazon.com/images/I/71yD3H2jl6L._AC_SL1500_.jpg

It is possible IDEMITSU updated formulation in never batches that now has SP certification - https://images-na.ssl-images-amazon.com/images/I/71sZb9m9AEL._AC_SL1500_.jpg
This is what they say about LSPI and how they deal with it:
  • Optimized detergent chemistry eliminates LSPI (also known as stochastic pre-ignition) events, most common in certain TGDI vehicles operating at low speeds and high loads"

Subaru recommends API SN rated motor oil for CT (this is what I bought), this may be inadequate to block LSPI in normally operating 2.5L engines though.
 

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Finally got oil well above 196 F - and it is knocking unapologetically on any slow acceleration and 1000-2000 RPM. So SP oil is not capable of stopping LSPI - meaning engine is operating outside of the normal. Will swap EGR once I receive it. So 196 F is the key temperature for knocking to start or at least become noticeable. The only issue - oil stays at this temperature for short period of time. Maybe in the summer - it will be staying above 196 F for longer time, so reproducing it would not be an issue.
 

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Finally got oil well above 196 F - and it is knocking unapologetically on any slow acceleration and 1000-2000 RPM. So SP oil is not capable of stopping LSPI - meaning engine is operating outside of the normal. Will swap EGR once I receive it. So 196 F is the key temperature for knocking to start or at least become noticeable. The only issue - oil stays at this temperature for short period of time. Maybe in the summer - it will be staying above 196 F for longer time, so reproducing it would not be an issue.
It needs to be at least 196 F in order to hear it. But usually oil temp would peak around 212 F. After I got the new EGR it doesn’t sit at those high temps anymore. A couple days ago I was driving in stop and go traffic and the engine oil temp peak at almost 212 F, once I started to get moving again the temp dropped right away. With the old EGR it didn’t do that, and it allowed the engine oil temp to sit at that high temp longer than usual.
 

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I wonder how many Subaru’s are having EGR issues with the 2.5 & 2.0 boxer engines. Doesn’t really look good on a brand to have this type of issue when a car is so new... I can understand if they have lots of mileage and have aged over time since they would get dirty carbon.

I’m curious about the 2.5 because those are found in the Forester, Legacy, Outback, and Crosstrek. If the 2.5 in the Crosstrek is having this issue, it doesn’t show me confidence in the brand because that means those other models could have the same issue as well. Hopefully Subaru is aware of this problem. Maybe it could be an EGR issue during the build process?
 
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