Subaru H4 piston soak possible?

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PhilloBeddow

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Oct 19, 2024
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Lexington, KY
2014 Subaru legacy FB25 6MT, 95000 miles, owned since new.

Short block replaced under warranty at 50000 miles because of excessive oil consumption. Spark plugs replaced at same time just because. Iridiums.

Oil consumption is … ok I guess but still there. My annual mileage about halved when I retired to about 6-7k / year and I’m on the severe OCI schedule as I do a lot of in-town driving.

Currently close to the end of my first 0W-20 VRP OCI and oil consumption seems somewhat reduced but hard to quantify. I’ll be staying with VRP for the next few OCIs. I’m aware 5W-30 will probably reduce oil consumption but I want a baseline for comparison, hence Subaru recommended 0W-20 for the first few OCIs.

Gas is usually Costco Top Tier and the 2014 legacy is port injected (MY2018 was when the Legacy went GDI I believe) so I don’t anticipate valve carbon build up being a problem.

That’s the background. Here’s my question -

Is a piston soak feasible for a flat 4 engine ? Notwithstanding the difficulty of getting to the spark plugs how would you soak the rings evenly?

The only way I can think to do that is to lay an old mattress down and flip the car on its side. I don’t want to do that because my wife will want the extra garage space and then I’ll have to park like that all the time.

Would adding Berrymans B-12 to the gas tank help if I’m already using Top Tier?

I want to minimize the oil consumption as best I can going forwards but I think I might already be past the point of diminishing returns and I don’t want to be an idiot about it.

What say you all?
 
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That gen is known to use oil from the low tension rings not really an issue that shortens engine life esp. since beginning in 2014 there was a low oil level light.
Not possible to do piston soak... at least not in a reasonably easy way.
 
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I need to do a '15 Forester. Was contemplating either the Seafoam spray-in-the-intake OR has anyone ever run the pressure pot fuel injector cleaners on these?

@clinebarger ever done a Subaru?
 
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finish up the 0w-20 Valvoline R&P,then try 5w-30 R&P for at least three or four 4k changes and a Fram ultra filter each OC, some nice highway runs may be good to do , and add some Techron fuel system cleaner right before each oil change plus replace the PCV valve , & , this viscosity 5w-30 would be fine for your climate in KY.
 
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Your best bet, but I heard they changed the formula, would be to obtain a quart of Kreen. Follow the directions- I think it’s half in the oil and the other half in the gas. Then drive 1000 miles and repeat if necessary. I’ve not used it since the formula change, but you can find an entire library on it here.

I’ve never had a ‘14, but I do maintain my mom’s ‘18 FB25. It doesn’t use a drop during the OCIs, the last was 16k on HPL PCMO and it was still right at the top mark on the stick.

If it were mine, I’d start with the Kreen. If you can’t get it, B12 would be my 2nd choice. You don’t drive when you put B12 in the crankcase like you do with Kreen, so follow the directions. After that, or even in the meantime, I’d go up at least one grade, but also maybe try an OCI with a PAO or POE-based oil since the “true” synthetics will have a higher evaporation temp and should combine with the thicker oil to reduce consumption. You’d really be best to do the B12 in oil in your existing fill, change it once with your cheaper choice, do a 2nd round in 500-1000 miles, and then go to the “true” synthetic. If the synthetic doesn’t curb oil use, go back to a VML-type and maybe even a 40 grade- it doesn’t bother these motors at all. M1 FS 0w40 is always a great choice. Best of luck!
 
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facility1 said:
finish up the 0w-20 Valvoline R&P,then try 5w-30 R&P for at least three or four 4k changes and a Fram ultra filter each OC, some nice highway runs may be good to do , and add some Techron fuel system cleaner right before each oil change plus replace the PCV valve , & , this viscosity 5w-30 would be fine for your climate in KY.
Click to expand...
Thanks for the suggestions. That’s pretty well aligned with what I’m thinking. Already using the Fram Ultra.

This week isn’t the time to switch from 0W to a 5W though it’s going to be cold 😳

1736052249131.webp
 
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SubieRubyRoo said:
Your best bet, but I heard they changed the formula, would be to obtain a quart of Kreen. Follow the directions- I think it’s half in the oil and the other half in the gas. Then drive 1000 miles and repeat if necessary. I’ve not used it since the formula change, but you can find an entire library on it here.

I’ve never had a ‘14, but I do maintain my mom’s ‘18 FB25. It doesn’t use a drop during the OCIs, the last was 16k on HPL PCMO and it was still right at the top mark on the stick.

If it were mine, I’d start with the Kreen. If you can’t get it, B12 would be my 2nd choice. You don’t drive when you put B12 in the crankcase like you do with Kreen, so follow the directions. After that, or even in the meantime, I’d go up at least one grade, but also maybe try an OCI with a PAO or POE-based oil since the “true” synthetics will have a higher evaporation temp and should combine with the thicker oil to reduce consumption. You’d really be best to do the B12 in oil in your existing fill, change it once with your cheaper choice, do a 2nd round in 500-1000 miles, and then go to the “true” synthetic. If the synthetic doesn’t curb oil use, go back to a VML-type and maybe even a 40 grade- it doesn’t bother these motors at all. M1 FS 0w40 is always a great choice. Best of luck!
Click to expand...
Thanks. I’ll look into Kreen.

As others have posted elsewhere, if you change two variables at the same time you’re never sure which one has an effect. I’m not in a rush but that might be next.
 
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Ranger83 said:
What Subarus have you owned?
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G

Thread '2012 Subaru Legacy 2.5 N/A CVT 266k Kms'

This is going to be my new DD. I've never owned a Subaru, so I'm looking for some advice and tips. I'm going over it to get it road worthy and so far it needs, ball joints, pads and rotors, tires, LCA bushings and the LF window won't go down. The car has been sitting for two years after the CVT failed. The CVT was replaced with a USED unit however, the car never went back on the road. I've started replacing some of the aforementioned parts and while doing so, I noticed broken engine ground harnesses, which I've started fabricating. Thanks in advance for your suggestions.
  • Wow
 
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GSCJR said:
G

Thread '2012 Subaru Legacy 2.5 N/A CVT 266k Kms'

This is going to be my new DD. I've never owned a Subaru, so I'm looking for some advice and tips. I'm going over it to get it road worthy and so far it needs, ball joints, pads and rotors, tires, LCA bushings and the LF window won't go down. The car has been sitting for two years after the CVT failed. The CVT was replaced with a USED unit however, the car never went back on the road. I've started replacing some of the aforementioned parts and while doing so, I noticed broken engine ground harnesses, which I've started fabricating. Thanks in advance for your suggestions.
  • Wow
Click to expand...

I give you credit for persistence!
GSCJR said:
I paid $2000 for it and I budgeted an additional $1000 in parts/repairs.
Click to expand...
 
Last edited:
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97prizm said:
Can you do a double dose of bg44k?
Click to expand...
This isn't mine but I need a one and done approach.

I think the pressure pot will clean injectors (kinda the point, and I realize not really the target here) and rings but not so much valves -- at least not intake valves. Still, seems a more elegant solution.

The Seafoam would more so do valves and rings since it goes through the intake.

I've previously rigged an FB to run on my pot, so if I can remember how I did it I think I'll try again, but with proper "hot" cleaner:
Post in thread 'Subaru FB25 - misfires and O2 sensor?' https://bobistheoilguy.com/forums/threads/subaru-fb25-misfires-and-o2-sensor.378857/post-6779783
 
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