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Discussion Starter · #1 ·
I am not a big fan of running direct injection engines without at least one catch can, so I bought a kit from Mishimoto for a 21 2 liter and adapted it to my 21 sport 2.5 liter. I had to modify the bracket that came in the kit. The holes that they recommend to use are there, but on the Sport there are A/C lines in the way. I drilled a hole about in the middle of the bracket. This allowed me to mount the bracket behind a plastic cover lower on the firewall. I checked to make sure there wasn’t anything behind the cover where the bolt I used was. The cover holds the bracket on one leg of it to level it and keep it that way. The line that goes to the Crank case vent and intake manifold is 1/2” ID. The catch can is 3/8. A reducer was made to combat this problem. Some say these are not needed. I say better safe than sorry. They (I had two)worked on my 17 WRX, so I’m a believer in the need for this. Pics….
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I also use the Mishimoto in my 17 which is not direct injection, but figure the same as you about being safe than sorry and trying to keep the upper engine as clean as possible.
Almost nothing collects in the summer but winter weather requires emptying every 2 weeks.

Your install look good!(y)
 

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I still don't get the "catch can" thing. How much snake oil does it catch versus the cost and maintenance, over the lifetime of the engine? 😸
 

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It depends how hard you drive your Crosstrek, if you drive mostly below 3k rpm, the catch can may not catch much. However if you often drive beyond 4.5k rpm, definitely you will see up to 10 fl oz oil inside.
 

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OK, and over how many miles and how much of that will result in carbon deposits in your engine? All I've ever seen is how much was captured (miniscule amounts) not how the engine was saved.

I still think it's snake oil capture... 😸
 

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I was going to put a Crawford AOS on my new '21 when it arrives. However, after talking with Crawford, they do not recommend it for winter use due to the chance of it freezing up. Then I talked to my buddy who had one on his '19 Colorado diesel and his froze up this past March. This caused the rear main seal to burp out oil all over. He removed it and so far there was no permanent damage done. As it has not leaked since removing it.
 

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Me too. I have yet to see proof of them doing anything. Not an argument...In fact I bought one. I never installed it bc I found that there was no info supporting their usefulness.
 

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Discussion Starter · #10 · (Edited)
I still don't get the "catch can" thing. How much snake oil does it catch versus the cost and maintenance, over the lifetime of the engine? 😸
Not trying to debate. Just my observation……… in a multi port injected engine….. no benefits what so ever, since all the intake goes through the valves. The detergent in today’s gasoline’s keep the intake tract clean. The small amount of blow by gets recycled and burned.
a direct injection intake system only flows air into the cylinder Through the manifold. The injectors feed the chamber fuel. The small amount of blow by goes into the intake manifold, into the air stream and goes over its intake valve. Some burns off in the cylinder, some stays on the back of the intake valve and collects over time on the back side of the valve in the form of carbon build up. It WILL eventually need to be cleaned via chemical cleaning(not the best method) or a blasting. That process is expensive unless you know how to do it yourself and have the equipment to do it. The can collects the blow by that goes through the crank case vent valve. The can maintenance is much more simple than a walnut blasting. On my 17 WRX I emptied the cans every other oil change. Very little came out, but that was oil/water not getting to cover the backsides of my intake valves. I was able to get a scope in to check out the intake valves. There was very little carbon collected on the valves. I always use the oil weight called for. Synthetic, dextros low volatility oil (Enos), and it is changed every 4,000 miles along with a factory, NAPA gold or Wix filter(I do the same for my 21 2.5 liter Crosstrek, in fact it has 5,500 miles on it and the oil has been changed three times. next change will be at 9,000 miles.) I did DRIVE my WRX, shifts at 6,000 rpm, and cruised at 4,500 - 5,500 rpm. My Crosstrek is driven mostly in Manual/sport mode with shifts at 5,500 rpm and cruise at 2,500 rpm, so it gets driven harder than most I think. I will scope the intake valves at 10,000 miles and see how effective the can is. There cannot be any harm in running the can.
you have your opinion, I have mine that is all….🤷🏼‍♂️
 

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This is how Scotty Kilmer cleans intake valves.

 
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Discussion Starter · #12 ·
I did it that way once on my WRX. IT RAN FUNKY FOR ABOUT 150 miles. Never did it again. Installed two boomba racing catch cans.
This is how Scotty Kilmer cleans intake valves.

[/Q
 

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Discussion Starter · #13 · (Edited)
I emailed Mishimoto and told them how I adapted the catch can for 2.0 liter Crosstrek to a 2.5 liter Crosstrek Sport. I sent the pics I posted. They emailed me back the next day and said they were aware of the changes to the 2021 2.5 liter, and they were working on a kit for it. I told them the only REAL issues are the bracket and the barb fittings. I let them know how I reduced the hoses to make things work. I got an email asking for my address so they could send me two barb fittings for the can that have 1/2” barbs. Also said when they have a bracket, they will be sure to send me one of those as well………. I’d say that is EXCELLENT customer service!
 
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OK, and over how many miles and how much of that will result in carbon deposits in your engine? All I've ever seen is how much was captured (miniscule amounts) not how the engine was saved.

I still think it's snake oil capture... 😸
Agree. There is also some technical evidence or theories out there I’ve read on Bob’s oil pages the can can do more harm than good. Modern premium 0W-20 has a lot of synthetic chemicals that are in the oil vapour that have some cleaning effect on the intake similar to the fuel. Not same effect as fuel. But designed to reduce carbon buildup. And the can is stopping that. The problem is there are two arguments thrown around. Lower NOACK oil means lower vapour and potentially lower deposits in theory But higher NOACK means higher vapour and a cleaning effect on the intake. But oil vapour and oil mist are not the same. I feel it should be higher vapour and low oil mist as the best property for oil I think. Many premium oils have these properties. Do the research. Many don’t. Either way the catch can is filtering out the stuff the oil companies put in the oil to try and reduce carbon buildup. Subaru knows this I would have though. A bit like your water filter jug in the fridge filtering your tap water. Your teeth don’t get the fluoride….

EDIT: NOAK changed to NOACK
 

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Agree. There is also some technical evidence or theories out there I’ve read on Bob’s oil pages the can can do more harm than good. Modern premium 0W-20 has a lot of synthetic chemicals that are in the oil vapour that have some cleaning effect on the intake similar to the fuel. Not same effect as fuel. But designed to reduce carbon buildup. And the can is stopping that. The problem is there are two arguments thrown around. Lower NOAK oil means lower vapour and potentially lower deposits in theory But higher NOAK means higher vapour and a cleaning effect on the intake. But oil vapour and oil mist are not the same. I feel it should be higher vapour and low oil mist as the best property for oil I think. Many premium oils have these properties. Do the research. Many don’t. Either way the catch can is filtering out the stuff the oil companies put in the oil to try and reduce carbon buildup. Subaru knows this I would have though. A bit like your water filter jug in the fridge filtering your tap water. Your teeth don’t get the fluoride….
I've been doing some research on the oil I plan on running.....Motul 8100 Eco-Lite 0w20. As far as I can tell, it's a good oil and has the newest API SP rating. The SP rating is geared towards GDI engines and trying to keep them clean.
 

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Part 2 from above...

0W-20 is known for having a higher NOACK than heavier weight oils. More oil vapour. That is part of the reason why GDI engines use that weight (I believe) So using a heavier weight is reducing the vapour and cleaning effect on your intake. Using a 5W-30 is lowering the NOACK and increasing the potential for carbon deposits to build up on the intake valves. Hey but that is just my view. I know many would disagree.
 

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They are beneficial.


Seems like a lot more people don't understand engines here and refuse to accept evidence. There is no snake oil involved here. Not only does the video cover oil catch cans, it also outlines the problems with DI engines, and the core differences between engines and why manufacturers are going with different solutions. An oil catch can is just another preventative measure, plain and simple. Some people don't want to pay extra for better fuel, some people want to follow every detail of a manual because it's "recommended", other people understand that preventative maintenances won't be in the best interest of those writing the manuals that come with your vehicle. They just want to cover their asses through a warranty and the rest is on you.

It's generally always the same people on this forum asking for evidence and causing a debate. It's unnecessary. What someone does to their engine does not effect you. Let them add as many oil catch cans and change their oil as often as they want. The evidence for preventative maintenance is all over the place - and certainly NOT in a scotty kilmer video. Ever. Yes, I have seen him cover Subaru engines - it's his so called "experience" that's the scam, and the way he conducts his channel equally so. I'd rather ask ChrisFix about literally anything than to give Scotty Kilmer one minute worth of viewing revenue.
 

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LmFAOOOOOOOOOO Scotty Kilmer should NEVER be quoted or taken as honest, intellectual, intelligent, or well researched information. That man is a moron and is wrong more often than right.
LOL, I can't even stand to listen to a few seconds. I'm astonished he has so many views...
 
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