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2020 Forester Premium
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An old timer back when things were simple told me a full tank of high test(high octane) mobil, BP, Shell and drive at highway speeds for 50 miles use up the tank and refill with regular low octane maybe this might help.
 

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Sahuarita, Arizona USA 2018 Forester Limited
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Seafoam is OK; however, alternately using a heavy solvent, like Berryman B12 chemtool and later something with a high concentration of Poly Ether Amine (PEA) will work wonders IF there is any buildup. High-PEA cleaners include Gumout w/ regane (they actually label their products that contain PEA now), Redline SI-1, Chevron Techron and several others that I don't use.
CRC 1 Tank claims to have the highest concentration of PEA on the market:
 

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Hi, the dealer said I had "carbon buildup on my engine" and recommended removal using the "Engine maintenance kit". It apparently comprises:

Fuel Injector Cleaner (SOA868V9150), a gas tank additive that cleans fuel injectors and intake valves without disassembly
Throttle Plate and Induction Cleaner (SOA868V9170), a high-pressure aerosol chemical mist that cleans throttle plate and idle air controller components, and
Top Engine Cleaner (SOA868V9160), a mist that removes soft carbon deposits from the intake plenum and valves, upper cylinders, and compression rings. Application requires Top Engine Cleaner Tool (SOA868V9430).
• Cleans fuel/air induction systems
• Removes soft carbon deposits
• Improves idle and fuel mileage
• Restores lost power and acceleration
• Reduces emissions
• Safe for oxygen-sensors/catalytic converters

I thought I read that you can't clean [intake valves?] from the inside because they never come into contact with the inside, and you need to do a walnut something or manually remove and scrape [only parroting random bits I remember reading, I have no idea what I'm talking about]. What additional questions should I ask the guy to better understand what needs to be cleaned and what I should do?

Thanks so much,
GES
I have had a tremendous amount of fortune with Lucas oil gas treatment, use it consistently inyour car (every fuel fillup) and you won’t get a carbon buildup! Yes it works I’ve seen the evidence !
 

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Hi, the dealer said I had "carbon buildup on my engine" and recommended removal using the "Engine maintenance kit". It apparently comprises:

Fuel Injector Cleaner (SOA868V9150), a gas tank additive that cleans fuel injectors and intake valves without disassembly
Throttle Plate and Induction Cleaner (SOA868V9170), a high-pressure aerosol chemical mist that cleans throttle plate and idle air controller components, and
Top Engine Cleaner (SOA868V9160), a mist that removes soft carbon deposits from the intake plenum and valves, upper cylinders, and compression rings. Application requires Top Engine Cleaner Tool (SOA868V9430).
• Cleans fuel/air induction systems
• Removes soft carbon deposits
• Improves idle and fuel mileage
• Restores lost power and acceleration
• Reduces emissions
• Safe for oxygen-sensors/catalytic converters

I thought I read that you can't clean [intake valves?] from the inside because they never come into contact with the inside, and you need to do a walnut something or manually remove and scrape [only parroting random bits I remember reading, I have no idea what I'm talking about]. What additional questions should I ask the guy to better understand what needs to be cleaned and what I should do?

Thanks so much,
GES
Induction clean should be done about every 30,000 miles.
If a piece brakes off its sound like a rod knocking for a short time.
I have experienced this. I ran the induction cleaner from BG. Worked great
Should have seen the carbon crap come out of my exhaust on the test drive.
Also helps to use top tier fuel like Chevron and use 44k by BG.
 

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Hi, the dealer said I had "carbon buildup on my engine" and recommended removal using the "Engine maintenance kit". It apparently comprises:

Fuel Injector Cleaner (SOA868V9150), a gas tank additive that cleans fuel injectors and intake valves without disassembly
Throttle Plate and Induction Cleaner (SOA868V9170), a high-pressure aerosol chemical mist that cleans throttle plate and idle air controller components, and
Top Engine Cleaner (SOA868V9160), a mist that removes soft carbon deposits from the intake plenum and valves, upper cylinders, and compression rings. Application requires Top Engine Cleaner Tool (SOA868V9430).
• Cleans fuel/air induction systems
• Removes soft carbon deposits
• Improves idle and fuel mileage
• Restores lost power and acceleration
• Reduces emissions
• Safe for oxygen-sensors/catalytic converters

I thought I read that you can't clean [intake valves?] from the inside because they never come into contact with the inside, and you need to do a walnut something or manually remove and scrape [only parroting random bits I remember reading, I have no idea what I'm talking about]. What additional questions should I ask the guy to better understand what needs to be cleaned and what I should do?

Thanks so much,
GES
Yes, it is a good idea to do a top end clean on any boxer engine. You can do it yourself easily. The genuine fuel additive can be bought, along with the spray can of top end cleaner, from your Subaru dealer.
Adding the injector clean into a near full tank of fuel is all you have to do. Then best to do a nice freeway drive and let it do it's thing.
The spray is delivered into a warm engine through a port in the intake manifold. You under the bonnet spraying it in, and an assistant holding the rev's at about 2000rpm. The Dealer will show you which vacuum line to disconnect or go to Google.
So easy to do so why pay the Dealer? Also, you will probably do a more thorough job as well.
The spray solution MUST go past the inlet valves and so must do some sort of cleaning. The other walnut thing?? Never heard of it but you can't manually scape valves without direct access.
Throttle body cleaning can be done at home if you have a bit of extra knowledge. Cable operated throttles are less risky than fly by wire systems.
So unless you have that extra knowledge, stick to the fuel additive and top end spray. Those two things will make a noticeable difference. Good luck!
 

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2001 Forester
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The other walnut thing?? Never heard of it but you can't manually scape valves without direct access.
It's called walnut shell blasting. It's a common process developed to combat carbon build-up on GDI intake valves. Do a search on youtube, plenty of videos about.
 

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2015 Forester
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82 Posts
An old timer back when things were simple told me a full tank of high test(high octane) mobil, BP, Shell and drive at highway speeds for 50 miles use up the tank and refill with regular low octane maybe this might help.
Back when they actually made high test (leaded gas), I think this was true as it had stuff to boost power (a lot of stuff that is now banned, I think) along with octane. Modern fuels are simply octane boosters with maybe a little extra cleaning additives. A couple of independent reports I've seen didn't seem to conclude the cleaners were significant enough to do anything and your better off buying your own additive cleaner.
 

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2015 Forester 2.5i CVT
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I actually paid to have this service done at the dealer in my 2015 2.5i. Yes I am sure I over paid for what the service is. I was happy with the results. I did it for the first and currently only time at 90k and haven’t heard anything about this before then. I could easily feel a difference in idle and performance. Was it worth my time and money? Yes I think it was.

Now could I have done it myself? I am sure I could have. Did I have the time to do it myself at the time, not really.
 

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2001 Forester
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This sounds like a crock of s$#t to me!
It's all over the internet carbon buildup is real, the early implementations were bad, ie Audi, BMW, required walnut blasting with engines reaching around 50,000 miles!!!.

Some companies, like Toyota are now moving towards a hybrid style of injection, their engines have both port injection and DI. The port injection is used at certain times and the DI is used at other times. The combination helps keep the intake valves from carbon buildup.

Ford and several other companies claim they don't need the port injectors by adjusting the valve timing such that the DI will spray some fuel onto the intake valves to keep them clean.
 

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Yes, it is a good idea to do a top end clean on any boxer engine. You can do it yourself easily. The genuine fuel additive can be bought, along with the spray can of top end cleaner, from your Subaru dealer.
Adding the injector clean into a near full tank of fuel is all you have to do. Then best to do a nice freeway drive and let it do it's thing.
The spray is delivered into a warm engine through a port in the intake manifold. You under the bonnet spraying it in, and an assistant holding the rev's at about 2000rpm. The Dealer will show you which vacuum line to disconnect or go to Google.
So easy to do so why pay the Dealer? Also, you will probably do a more thorough job as well.
The spray solution MUST go past the inlet valves and so must do some sort of cleaning. The other walnut thing?? Never heard of it but you can't manually scape valves without direct access.
Throttle body cleaning can be done at home if you have a bit of extra knowledge. Cable operated throttles are less risky than fly by wire systems.
So unless you have that extra knowledge, stick to the fuel additive and top end spray. Those two things will make a noticeable difference. Good luck!
The walnut clean involves taking off the intake manifold
 

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2015 Forester CVT
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666 Posts
DIT engines the fuel doesnt flow over the valves. seafoam wont do anything for OPs issue. They makes a GDI cleaner but it doesn't work as well as walnut blasting.
TheFB25 is not a direct injection engine so that is not a consideration in this thread, right?

GD
 

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Sahuarita, Arizona USA 2018 Forester Limited
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The Forester engine went to direct injection beginning in model year 2019.
 

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Sahuarita, Arizona USA 2018 Forester Limited
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Make sure you get the more expensive Techron- Complete Fuel System Cleaner (cheaper one is just diluted version).
Thanks, I didn't realize that.
 

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2014 Forester Touring 2.5 CVT
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Since your engine isn't direct injection, you might want to do a Tecron mega treatment which I have done on every car I have owned even though I can't say it ever made a noticeable difference. Wait until it's time to change the oil and dump a can or two even of Tecron into a quarter tank of fuel and drive the engine hard (which may be the best cure for a coked up engine by itself) and then fill up the tank and change the oil after burning the treated fuel. I'm not a chemist, but I think Stoddard's solvent is the majic stuff in most fuel cleaners and Tecron was/is considered the best stuff. Anyway, if you follow the directions on the bottle you'll only be getting what you would with a fill up of Chevron gas. I think all gasoline is basically from the same pipeline and the brand difference is in the additives the tanker truck driver dumps in during his refuel of the station's tank and Tecron is what makes Chevron such good fuel.
 

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2013/14 2.5i-L CVT
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Fuel Injector Cleaner (SOA868V9150), a gas tank additive that cleans fuel injectors and intake valves without disassembly
Throttle Plate and Induction Cleaner (SOA868V9170), a high-pressure aerosol chemical mist that cleans throttle plate and idle air controller components, and
Top Engine Cleaner (SOA868V9160), a mist that removes soft carbon deposits from the intake plenum and valves, upper cylinders, and compression rings. Application requires Top Engine Cleaner Tool (SOA868V9430).
Fwiw, Subaru AU requires the injector cleaner and top/upper cylinder cleaner be applied at every service during the warranty period for both N/A and turbo engines. Have done for over a decade.
 
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