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2010 Forester Premium X AT
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Discussion Starter #1
205,000 mi on the clock. Mileage is meh and i've never done a top engine cleaning for it. I feel like a top engine cleaning is probably worth it if its not too difficult but I hate to mess up any sensors. I'm not really seeing any good writeups for foresters. Has anyone used the subaru top engine mist cleaning, or seafoam through a vaccum port who can give some details?
 

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2016 2009 Subaru WRX
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205,000 mi on the clock. Mileage is meh and i've never done a top engine cleaning for it. I feel like a top engine cleaning is probably worth it if its not too difficult but I hate to mess up any sensors. I'm not really seeing any good writeups for foresters. Has anyone used the subaru top engine mist cleaning, or seafoam through a vaccum port who can give some details?


I wouldn’t bother, you have port injection. The newer Subaru’s with direction need it because the fuel doesn’t wash the intake valves.


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2019 Crosstrek 2018 XT
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I would put a can of sea foam in for sever all thankfully. My subaru Tec has been In th business 35 years swears by it
 

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‘14 FXTT; '15 Legacy FB25
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I would put a can of sea foam in for several tankfulls. My subaru Tech has been In the business 35 years swears by it
Fixed your auto-corrects.

I disagree. I'd rather add something with a large quantity of PEA than some solvent.

Chevron Techron
Gumout w/ Regane (Gumout now lists which bottles contain PEA)
Redline SI-1

I'm sure there are others, but these have been my go-to.

Chevron is actually on-sale on Amazon for seven bucks:
 

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2005 Forester Automatic
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495 Posts
Well, I learned a long time ago that things that are working should not be messed with. If your 10' with over 200k miles is doing well, I'd very much avoid any and all things even the least bit radical. You will only regret it.

Of course, things like a tranny fluid exchange, timing belt and idlers are of course widely agreed as needed. But snake oil additives or even legit cleaners added to a well functioning engine are a recipe for failure....
 

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Discussion Starter #6
I'll provide you a data point from my 2002 forester. I was pretty religious about seafoam and techtron into the gas tank for 100,000mi and when the head gaskets were replaced due to external weeping, I had the heads pulled and I was really surprised at how much carbon there was on the valves. Hence, I have a hunch that fuel system cleaners are good for getting water and contaminate buildup out of the tanks, but they are not effective in removing carbon buildup on the top end.
 

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‘14 FXTT; '15 Legacy FB25
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I'll provide you a data point from my 2002 forester. I was pretty religious about seafoam and techtron into the gas tank for 100,000mi and when the head gaskets were replaced due to external weeping, I had the heads pulled and I was really surprised at how much carbon there was on the valves. Hence, I have a hunch that fuel system cleaners are good for getting water and contaminate buildup out of the tanks, but they are not effective in removing carbon buildup on the top end.
Did you use top-tier fuel?

How often did you use cleaner?

I wonder how much worse your valves would have looked without the using Techron. I don't think Seafoam does much of anything in the gas tank.
 

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Discussion Starter #8
Yep, I was typically using Shell or Mobil gas stations in the midwest at that time. I was using a bottle in the tank once a month. Felt like it was a huge waste of money when I saw those heads.


Anyway, if anyone has any experience with top end cleaning on this vintage, let me know.
 

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2015 Forester CVT
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665 Posts
Where does the contamination come from

I wouldn’t bother, you have port injection. The newer Subaru’s with direction need it because the fuel doesn’t wash the intake valves.


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I used to think that the "valve washing" concept made sense until I realized that there is no source of contamination upstream of the valves unless the valve seals are shot or something else is not functioning correctly. Even in some older engines with EGR that I have overhauled did not have significantly dirty valves.

GD
 

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Discussion Starter #10
I think the contamination comes from oil vapor that gets sucked back into the intake via at least the PCV system, and maybe one other.
 
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