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2004 Subaru Forester XT
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Discussion Starter · #1 ·
Hi y’all. I am about to change the oil for the first time on my FXT. It has 187k miles and has always used conventional oil.

I’ve found conflicting reports on the use of conventional vs synthetic oils. Some say synthetic oil runs better in a turbo engine. I’ve also read about instances where turbos have failed after switching to synthetic, and in turn switched back and gained better engine performance.

Originally I was going to go with an OEM oil filter but I’ve also seen conflicting reports on the integrity of these filters.

Your knowledge and recommendations are much appreciated. Thanks!
 

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2004 Forester XT Auto
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313 Posts
You can research oil for countless hours and get nowhere, since there is so little actual data and so much armchair engineering and hearsay. However, things that are generally true are that newer oil specs are not necessarily better for older cars, and that thicker oil will in general protect the engine more. Also that a "heavy duty" oil will have a better additive package and viscosity than a standard oil of similar grade, and that the conditions in a turbocharger are known to be very hard on oil and cause shear and heat thinning not found in NA applications.

Personally, I use Rotella T6 5w-40 in my turbo EJ's, motorcycle engines and small diesels, and it is widely regarded as a good choice by many in the turbo EJ community. For filters, I have lately been using Fram Ultraguards, but I used to use Purolators before they were bought out. OEM is also a good option, though keep in mind that OEM's can be constrained by cost considerations that enthusiasts are not.

One further thing is that there are multiple often sizes of filter that will fit a given application. I use Fram 7317 or Purolator PL14610, which is a longer than stock filter and has more media. I don't remember the application it's actually for, but it's definitely larger and fits perfectly.










inb4 I get flamed for oil choice :p
 

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2004 Subaru Forester XT
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9 Posts
Discussion Starter · #3 ·
You can research oil for countless hours and get nowhere, since there is so little actual data and so much armchair engineering and hearsay.
Believe me I have done just that! Thanks much for your input. It looks like it’s just going to be trial and error to see how my Forester reacts. I’m thinking I’ll stick with conventional and the 5w30 weight grade Subaru recommends in the manual. Just a matter of brand I suppose. I’ll be keeping a close eye on it anyhow.

I see from your profile that you have a 2” lift. Mind if I ask what kind of suspension you’re running? I’ve been thinking about a lift for mine as well.
 

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'14 Forester XT Touring
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573 Posts
...... another case of way overthinking oil and filters.
ANY oil is good enough. Oil filters, pick your poison oem or aftermarket.

Now the most important part of all of this:
Pick which fan boy-ism you want to be a part of.

I for one am a hardcore going on 15+ years Mobil 1 fan boy. I swing both ways on oil filters. Depends which is on sale. OEM or a Mobil 1 filter.
I can find Mobil 1 in any gas station, Walmart, or even a goodwill. Try that with some Royal (dip shat) Purple, or Motul.

Joking aside it doesn't matter which brand. Just make sure you have new clean oil and filter. Replace when needed.
 

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For the money, Castrol High Mileage blend and Wix filters are the best buy for me. Check out Consumer Reports and decide for yourself! There HAS been research done on motor oil. (Walmart has the oil, o'reilly the filter)
 
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2004 Subaru Forester XS
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17 Posts
Personally I use Pennzoil Platinum and WIX filters and have had good success from 90 degrees to -40 degrees in Alaska. My 04 is going on 200K and still going strong.
 

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2015 Forester 2.5i Limited CVT
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1,089 Posts
Mobil1 and Subaru Japan made OEM Black filter. # 15208AA160
OCI @ 3k miles.
Filter @ 5k mi.
8816D6E0-12FA-4E9A-B672-C89EAFA1F692.jpeg
A0C6683D-FCA7-42C2-9084-C8B05F01583B.jpeg
 

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2019 Crosstrek 2018 XT
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14,591 Posts
Oil is oil. Not much difference between syn/non syn. I wold be looking at 40 wt oil in your old XT.

Fram Ultra is the best filter but at the age of your rig it won't matter what you use.
 

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Don’t think you can go wrong with an OEM filter. Don’t know if I would switch to synthetic with the miles. How often do you plan on changing oil?


Sent from my iPhone using Tapatalk
 

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2007 2.5XT Limited 4EAT
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Generally speaking, as long as you aren't scraping the bottom of the barrel...ahem, literally in this case, any oil will get the job done. Same on the filter. I generally use the OEM blue ones or WIX. I have run Mobil 1 consistently in all my turbocharged vehicles for over 15 years with no complaints. Some folks won't touch the stuff. I recently started running Rotella T in my Foz and so far I haven't noticed a difference except for cost. While some will swear that it is liquid gold. Back in the olden days I was a Valvoline guy. Gold jacket, green jacket....you get the idea.
 

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2004 Subaru Forester XT
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Discussion Starter · #12 ·
Thanks for the input. To be honest I’m not so naive to think that brand makes a world of difference. No doubt each have different additives but like most have said, as long as it’s clean routinely changed. I was primarily interested in debate over synthetic vs conventional oil. I’ve also seen different opinions on the OEM Subaru filter.

I appreciate all the information y’all have gave. I wound up using Castrol GTX synthetic blend. I’m a strong believer in conventional oil but thought the additional synthetic base and additives. Recommended weight grade 5w30. OEM Subaru filter. I purchased the filter from a Subaru dealer with a crush washer and the washer didn’t fit the drain plug for some reason. Anyone ever encounter this issue?
 

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2017 Foz 2.5i CVT
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I believe Subaru used to use 20mm crush washers in the era of your 2004, and changed to 16mm a few years after that(?) Was the crush washer too small for your car? I might have this backwards though.

Good basic oil choice. It will give you a baseline on consumption. With the age and mileage of your car, I'd probably lean toward a high-mileage formula, like Castrol or Valvoline MaxLife, so if your engine uses some oil, maybe transition toward the high-mileage oil even when you're adding a quart.

And the syn blend basic oils like you used as well as the syn blend hi-mileage formulas are great.
 

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Motul 10-40 what I use, but in Australia, make sure you get the right one, ask the guy at the parts store, but MOTUL ALL DAY
Old subaru Love Motul oil
 

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2003 Forester
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107 Posts
Personally, I use Rotella T6 5w-40 in my turbo EJ's, motorcycle engines and small diesels, and it is widely regarded as a good choice by many in the turbo EJ community. For filters, I have lately been using Fram Ultraguards, but I used to use Purolators before they were bought out. OEM is also a good option, though keep in mind that OEM's can be constrained by cost considerations that enthusiasts are not.

One further thing is that there are multiple often sizes of filter that will fit a given application. I use Fram 7317 or Purolator PL14610, which is a longer than stock filter and has more media. I don't remember the application it's actually for, but it's definitely larger and fits perfectly.

inb4 I get flamed for oil choice :p

I run this same oil in all my cars and have for about 15 years. 600hp 535i, 450hp Galant VR4, 250hp Bug, EZ30 SG, Bone stock engine SH.

I personally think Fram filters are junk though. I'm almost positive the blue OEM Subaru filters in the US are made by Fram so I buy the black Tokyo-Roki ones online. If you want the longer filter with some more media in it to extend change intervals they are just from newer Subaru's. You can also use the OEM Mazda filter from an RX-8. These are what my friend runs on his OBXT. Made by Tokyo-Roki with the same dimensions as the longer Subaru filters. They don't recommend the EZ filter (Which is still made by Tokyo-Roki) as it doesn't have an anti drain back valve.

For the BMW and VW I use Mann and for the Galant I use OEM Mitsu.

Between all the vehicles I only do bi-annual changes. One spring one fall. I'd say that's between 3 and 10k miles depending on the car. Sent multiple samples into Blackstone labs and all engines come back as healthy with no signs of engine or turbo bearing material in them.
 

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2019 Crosstrek 2018 XT
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I personally think Fram filters are junk though.
They have the best filter rating bar none.

As far as Motul oil. Its good but used oul analysis says it is no bettert than Walmart Synthetic.
 

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2003 Forester
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They have the best filter rating bar none.
Source please. I'd love to have my mind changed.

I'm used to tear downs like this




 

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2019 Crosstrek 2018 XT
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14,591 Posts

Yes its a Fram filter site. But no other company will give you specs that mean anything. Most will filter in the 90% at around 30+ micron. Companies never give you an efficiency rating at a specified micron rating.

Lots of info here:
 

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2004 Subaru Forester XT
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Discussion Starter · #19 ·
I believe Subaru used to use 20mm crush washers in the era of your 2004, and changed to 16mm a few years after that(?) Was the crush washer too small for your car? I might have this backwards though.
The washer was too small. The guy at the parts counter even asked for my VIN to verify fitment because like you said, there were two different sizes. Makes me wonder if the oil pan was changed out or if it was just an error at the parts counter. Either way I'm retaining a good amount of oil with no leaks that I can see. Since I've bought the car I've watched the oil level fairly closely as well as any signs of leak or drip. There was no washer on the drain plug when I changed it so I should be fine until next oil change.

Also, the oil I used was indeed a high mileage solution. Castrol GTX High Mileage synthetic blend.
 

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1997 Legacy Outback 5MT
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You can’t go wrong any brand of 5w40 synthetic (don’t think 5w40 exists except as a synthetic) and a Subaru filter. As far as I know Subaru continues to use higher than normal bypass pressure valves in their filters. Not everyone agrees that this matters much, but many/most brands of filter are not going to have the factory bypass pressure. Subaru does or used to have two different height filters that were the same diameter, I would go for the taller one that holds a bit more oil.
 
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