2021 WRX STi - Switched from OEM oil to Motul X-clean EFE 5w30 - 19,685 miles
- Thread starter JVILLA
- Start date
Hi, all. I've been doing UOA's on my STi since about 5,000 miles. All of my UOAs are shown on the two posted documents. I was using the OEM oil until 14,615 miles. The numbers were good but it was consuming about a half quart every 1,500 miles so I would change the oil before I had to add another half quart during the OCI. I switched to Motul 5w30 for the two most recent OCIs and consumption went way down. The car also ran quieter and seemed happier. However, copper spiked to 50 and then 91. Should I be concerned? Blackstone seems to think so. I have another analysis waiting to come back with the Motul so we'll see what that shows.
I should also mention that on my current OCI, I am using Amsoil SS 5w30 since I am trying to stay with a 5w30 to maintain my warranty. The car seems a bit louder and is consuming more oil, probably due to the lower HTHS. It's making me want to switch back to the Motul but the copper levels with it were concerning. I've read that switching oils can cause copper to spike due to the oil cooler but they eventually come down. If this is the case, I'd like to switch back since the car seemed a lot happier. Or, do you all recommend any other 5W30s that meet Subaru's warranty specs? Thoughts on my numbers? The car is running great and I also had a compression/leakdown done back in February by a reputable shop and they said the numbers were good.
I should also mention that on my current OCI, I am using Amsoil SS 5w30 since I am trying to stay with a 5w30 to maintain my warranty. The car seems a bit louder and is consuming more oil, probably due to the lower HTHS. It's making me want to switch back to the Motul but the copper levels with it were concerning. I've read that switching oils can cause copper to spike due to the oil cooler but they eventually come down. If this is the case, I'd like to switch back since the car seemed a lot happier. Or, do you all recommend any other 5W30s that meet Subaru's warranty specs? Thoughts on my numbers? The car is running great and I also had a compression/leakdown done back in February by a reputable shop and they said the numbers were good.
dnewton3
Staff member
I'm not familiar with that engine and it's systems, but if it does have an oil cooler with copper brazing or copper tubing, then the Cu is likely the reaction to the add pack in the Motul. (It's not unheard of ... this was a common occurrence when people used certain oils in GM Duramax engines back in the day; it had a cooler with Cu brazing materials.) The reaction is harmless; it causes colloidal metals too small to be of concern to the engine, but they will show up in a UOA. The reaction will "normalize" over several OCIs and the numbers will drop off.
Swapping between oil brands frequently can cause these types of circumstances. While there's nothing "wrong" with doing so, it makes using UOAs more complicated as it is difficult to discern between "reactions" and true wear issues. The greatest concern is that one of these "reactions" would mask over a true problem, if a wear problem is present. If you get 90ppm of Cu in the UOA, how much of that is wear vs reaction? Is it 5 ppm of wear and 85 of reaction? This would be "normal" ... Or is it 40ppm of wear and 40 of reaction? That would indicate a problem is present ... There's no way to know.
Also, while rare, there could be an issue between competing additives when mixing some brands; many boutique lubes are very finely crafted and small shifts in additives might cause an adverse reaction.
I'm not saying it's dangerous to switch brands; I'm saying that doing so comes with concerns for potential issues and you have to be willing to accept the risks. The risks are more prominent when doing so with boutique brands, and less prominent with common OTC brands (as they generally don't have the unique additives which cause these kinds of reactions).
Swapping between oil brands frequently can cause these types of circumstances. While there's nothing "wrong" with doing so, it makes using UOAs more complicated as it is difficult to discern between "reactions" and true wear issues. The greatest concern is that one of these "reactions" would mask over a true problem, if a wear problem is present. If you get 90ppm of Cu in the UOA, how much of that is wear vs reaction? Is it 5 ppm of wear and 85 of reaction? This would be "normal" ... Or is it 40ppm of wear and 40 of reaction? That would indicate a problem is present ... There's no way to know.
Also, while rare, there could be an issue between competing additives when mixing some brands; many boutique lubes are very finely crafted and small shifts in additives might cause an adverse reaction.
I'm not saying it's dangerous to switch brands; I'm saying that doing so comes with concerns for potential issues and you have to be willing to accept the risks. The risks are more prominent when doing so with boutique brands, and less prominent with common OTC brands (as they generally don't have the unique additives which cause these kinds of reactions).
Looks like it "liked" the thinner oils in the first 4 reports. .02
edyvw
$50 site donor 2025
Apparently this is known issue on Subaru’s related to oil cooler.
Yeah, I’ve read similar things from different owners on different forums. It’s a benign issue, right? I’ll deal with it if it means less consumption. I’ll keep reporting back to see if the copper goes down.
Just the #'s. Odd that the OEM oil you used was, consistently thinner in the first 4 uoa's. I agree that more quiet and smooth is preferred by me..
Completely different engine, but here’s a uoa on an FA24DIT with a copper spike.
https://bobistheoilguy.com/forums/t...oci-copper-increase-oai-vs-blackstone.380613/
I ran many different oils in my ‘04 FXT and my copper never changed very much after the break-in metals washed out. Except for a couple of runs on SSO I also stuck with higher HTHS oils.
It does seem that there are more elevated Cu readings in turbo Subaru’s lately. I wonder if it’s an issue with the oil coolers?
https://bobistheoilguy.com/forums/t...oci-copper-increase-oai-vs-blackstone.380613/
I ran many different oils in my ‘04 FXT and my copper never changed very much after the break-in metals washed out. Except for a couple of runs on SSO I also stuck with higher HTHS oils.
It does seem that there are more elevated Cu readings in turbo Subaru’s lately. I wonder if it’s an issue with the oil coolers?
edyvw
$50 site donor 2025
It reacts to additives or base oil in Motul.
If you are paying for Motul, go X-Clean 0W30 EFE.
If you are paying for Motul, go X-Clean 0W30 EFE.
I’d like to stick with a 5w30 for warranty purposes.
edyvw
$50 site donor 2025
Ah ok.
Yeah, I saw that thread. It seems similar to my situation. I wonder if the oil coolers in both engines are the same or similar?
Your owner’s manual states that thicker viscosity is required for higher temps.
I looked up the part for my Outback and it lists the STI.
https://parts.subaru.com/p/Subaru__...-Oil-Cooler-Complete/49231148/21311AA051.html
Yeah, but the language is vague and says 5w40 can be used for replenishment only. I’d rather just use a robust 5w30.Your owner’s manual states that thicker viscosity is required for higher temps.
I looked up the part for my Outback and it lists the STI.
https://parts.subaru.com/p/Subaru__...-Oil-Cooler-Complete/49231148/21311AA051.html
That’s interesting about the oil cooler part number. Since this seems to be common with newer Subarus, I wonder if they used a different one for older ones? And if they did, could we swap them? At least for my EJ, it would work since it’s been around a billion years.
Been reading up on metals & Sulfur in the oil is one of the main culprits of Copper/Lead oxidizing causing these spikes. If that's what this is we don't know yet though. I'd stick to this oil for the next several runs to see how the Cu levels out. Hopefully it comes down. How do you drive this car out of curiosity?
Interesting. Does the Motul have a lot of sulfur?
It’s my daily. My commute to work is 10-15 minutes. I warm it up for about a minute in the morning before I start driving but I wait for it to fully warm up before getting on it. I don’t beat on it but I might drive spiritedly here and there.
The copper and the viscosity differences.
