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2019 Crosstrek 2018 XT
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The fuel does boil off as you drive but it is continuously rd introduced. Fuel molecules are smaller than oil. Enough of them remain even if you have the oil temp at 200F and then take a sample. It is checked with Gas Chromatography. Good question though. Should be less than 2
 

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2004 FXT / 2020 Outback Onyx XT
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1,679 Posts
I wish Subaru would’ve just gone with using the port and direct injection that’s used in the BRZ, but Subaru wanted to do it on their own.
 

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2019 Crosstrek 2018 XT
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14,712 Posts
Had the analysis at 4200 miles on my '18XT. The Viscosity really sheared back to a 20wt oil. The wear metals are fine so I'm OK with it. I will go to 7K miles and change this summer. Probably go with 10W-30
 

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2004 FXT / 2020 Outback Onyx XT
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What is the weight of the oil you had tested?
Guessing that it's 5W-30 since that's what's recommended and I know @adc has used 5W-30 in the past.

I don't believe this is all shearing and suspect some fuel dilution, but Blackstone only estimates fuel dilution. OAI FTW!

Funny that some of us new FA24DIT owners feel like guinea pigs running a 20 grade oil, when the operational viscosity of many FA20DIT's is a 20 grade anyway. It's not a common grade of oil used in these engines, as BS says, but the used oil usually comes back as a 20 grade with a Resource Conserving oil from shearing and/or fuel dilution.
 

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2018 Forester XT Touring - Blue
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18 Posts
Three tests under my belt now for the 18 FXT. Was changing my 5w/30 religiously every 3k miles, but Blackstone recommended 5-6k. Waited 5k this most recent time and their only comment was viscosity came up a little short of 5w/30 range - TBN was still good and "all looked well". They said to stick with 5k miles. Neat to know!

547516
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2018 Forester XT Touring - Blue
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First was "Subaru" brand for 3k miles - Second was Amazon 5w-30 for 3k miles (the Dexos 1 Gen 2 one) - which they said were pretty much identical. So the Third test was the Amazon 5w-30 for 5k miles.
 

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2019 Crosstrek 2018 XT
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Biggest issue with the XT is shearing down which is what you are seeing. My analysis above yours sheared down way worse than yours. I am putting in the 3 quarts of Supertech 10W-30 full syn and 2 quarts of 0W-40 Mobil 1. I intend to keep it in for at least 10K miles. But I will do analysis at say 8K miles.
 

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2004 FXT / 2020 Outback Onyx XT
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Biggest issue with the XT is shearing down which is what you are seeing. My analysis above yours sheared down way worse than yours. I am putting in the 3 quarts of Supertech 10W-30 full syn and 2 quarts of 0W-40 Mobil 1. I intend to keep it in for at least 10K miles. But I will do analysis at say 8K miles.
You're not concerned about intake valve deposits from the higher ZDDP or LSPI from the higher Ca with Mobil 1 0W-40? M1 0W-40 ESP should have lower levels, but probably harder to find and more expensive.

On the other hand, Subaru Japan still shows high SAPS Castrol 5W-40 on their web site for all turbos so I guess they're not too worried about IVD or LSPI either. 🤷‍♂️
 

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2019 Crosstrek 2018 XT
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The Intake valves will need a cleaning at 50K miles regardless of what oil you use (probably) i intend to do that.
 

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2021 Forester Premium CVT
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124 Posts
163,000 miles.
M1 High Mileage 5w-30.
4,944 miles on the oil, blue oem subaru filter.
3qt make up oil (had a 2,000 mile highway run on this sample and Techron in the tank at the time of this change)
547909
 

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2004 FXT / 2020 Outback Onyx XT
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1,679 Posts
163,000 miles.
M1 High Mileage 5w-30.
4,944 miles on the oil, blue oem subaru filter.
3qt make up oil (had a 2,000 mile highway run on this sample and Techron in the tank at the time of this change)
View attachment 547909
Wow, 3 quarts of make-up oil? Your car has a drinking problem. Hard to read the uoa given that the added oil may have helped wear metals and boosted the viscosity.
 

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2021 Forester Premium CVT
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Wow, 3 quarts of make-up oil? Your car has a drinking problem. Hard to read the uoa given that the added oil may have helped wear metals and boosted the viscosity.
Yeah just about 3 quarts, maybe a tiny bit less. That 2,000 mile run was high speed (Avg 80mph) and through the mountains of Tennessee. 2/3 of those quarts were used on that trip alone.
I keep a close eye on the level, and I always carry 2qts on hand. I can live with it.
 

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2004 FXT / 2020 Outback Onyx XT
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Yeah just about 3 quarts, maybe a tiny bit less. That 2,000 mile run was high speed (Avg 80mph) and through the mountains of Tennessee. 2/3 of those quarts were used on that trip alone.
I keep a close eye on the level, and I always carry 2qts on hand. I can live with it.
Sounds like my FXT. I switched to 10W-30, 10W-40, and a mix of the two to slow down my consumption. Winter is mainly 0W-40 with 10W-40 as a top-up.
 
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