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Understanding the needs of your new 2015 WRX/STi

184K views 332 replies 106 participants last post by  Nachos Libres  
#1 · (Edited)
This morning i've been lurking around IWSTI's section of 2015 related discussions and i've noticed the following:

- We have lots of new first time owners of Subarus (which is awesome!)
- Lots of misinformation is around
- Many of the new owners are completely ignoring the Subaru needs
- To summarize my point: There's lack of information on maintaing the Subaru motor to last as long as possible.

In this following post, I will try to outline everything I can, include everything I learned and please make sure to read the stickys on this forum to quickly answer any FAQ.

ENGINE:
- YOUR OIL YOUR OIL YOUR OIL YOUR OIL!
- Coolant
- Fuel

DRIVETRAIN:
- Transmission fluid (transmission, center and front diff are all in one)
- Rear diff fluid

MODIFICATIONS:
- What you should know


Engine - YOUR OIL:

From right now, i'll tell you to drop any previous "i've had great experience with brand x, so i'm sticking with it"
Turbocharged Boxer motors operate at a much higher temperature and they will shear any oil that can't handle heat too well. Your choice of oil will determine your odds of ringlands failure, oil burnt, spun rod bearings, etc etc etc.
The concept with the boxer motors is to use an oil that is able to handle heat and shear as minimum as possible.

Subaru recommends 5w30 and that's due to making their fuel mileage numbers look better...
Wait so does that mean Subaru isn't recommending the best type of oil for the car? Yes and no. 5w30 weight oil will suffice and do the job fine if you're driving from point A to point B with no spirited driving, you won't be seeing any AutoX or any track time. Just to leave this here for you, spirited/hard driving puts more load on your motor than an AutoX day - this is important to remember. Higher gears put higher load on the car, AutoX is usually gears 1 and 2 only.

Recommended brands, which have been proven time and time again to be the go-to:

- Shell Rotella T6 0w40 if you're in a cold climate, 5w40 or 10w40 if you're in a hotter climate
*NEW* - Amsoil now offers 0w40
- Amsoil signature 5w40
- Amsoil signature 10w40
- Mobil 1 0w30 or 5w30 (GERMAN/EUROPEAN SPEC)
- Castrol Edge 0w30 or 5w30 (GERMAN/EUROPEAN SPEC)
- Motul 8000 5w40
- Motul 300v
- Redline 5w40 or 10w40
- General rule of thumb, any Porsche approved oil is usually very well capable of dealing with our motors. Porsche has a much higher standard for parts and fluids.

Your choice of oil may change during winter vs summer, if you live in a cold climate, 0w30 is gives you a better start up viscosity versus 5w30 or 5w40.

Brands/models to avoid due to bad experiences, direct causation of engine failures:

- Royal Purple
- Mobil 1 USDM spec
- Castrol is iffy under USDM spec, 10w40 seems to farewell, 5w30 is inconsistent
- Gas station oil brands
- High odds of your dealer using bulk oil or department store synthetic oils to keep costs low.

Engine - Coolant:

- Subaru blue coolant is VERY good coolant, I recommend sticking to it.
- Stick to OEM thermostat opening levels unless you live in the middle east or near the equator line.

AVOID: Due to cooling problems time and time again while using such products.

- Additives
- Watter wetters


Engine - Fuel:

Use the best fuel you have available to you! 91Oct (Under the rating of RON+MON/2) is a minimum, 93/94 is highly recommended. If you click here you'll find a data logging table of 91 vs 94.



DRIVETRAIN:

Drivetrain - Transmission & rear differential fluids

Recommended fluids:
- Subaru Super S fluid
- Redline Shockproof
- Motul gear 300

- Subaru offers 2 options for transmission/rear diff, the regular fluid and the Subaru S (which isn't advertised) you will have to ask for the Subaru S fluid in specific to receive it. In Canada, they run at $10/litre.

- Your dealer *SHOULD* have Subaru S transmission oil, which is a phenomenal synthetic oil and costs roughly the same as other competitors (redline, motul, etc)

- Use the SAME transmission/diff fluid for the entire amount necessary; don't mix brands together to create a "cocktail", each brand have their own formula to their fluid and mixing brand x and brand m together may result in premature failure in the system.


MODIFICATIONS:

- ANYTHING you do that is power related, understand that you're under the possibility of having your warranty void. In the event which you're under the possibility of such outcome, understand that your dealer HAS TO PROVE your modifications were the DIRECT result of said failure.

- ECU alteration works through resetting the ECU many times over a small period of time, that's usually the indicator of a "modified ECU" - COBB Acessport only resets once, however, it's not invisible or undetectable. When a tuner tunes your car he/she adjust your parameters and reset and log, and repeat until what they see is what they like.


I wish you the best to your journey with your new 2015 WRX/STi.
 
#6 ·
Thanks, I just hope it helps out as many people as possible!


I've been using 5w-40 rotella in my 13 sti since the second oil change and I'm sticking with it. I only have about 9800 miles and it's not my daily so when I drive it it's driven hard. Burning zero oil and doesn't seem to get too dirty when I change it
Excellent choice.
 
#22 ·
I have been running Motul Gear 300 in the transmission for almost a year now and the car shifts significantly better than the Subaru fluid especially in the winter where in sub-zero temperatures there would be some 2nd gear nibble/grind when it was cold with the stock fluid. I actually feel this is the best modification I have made to my car do date and I am running Stg. 2 with a turbo back exhaust as there's something to be said for the joy of shifting a buttery smooth manual transmission.
 
#25 ·
Thanks for mentioning, i'll have to clarify the OP - Subaru S transmission fluid isn't their regular fluid - you will NOT receive the S fluid if you're in for regular maintenance, you WILL have to specifically ask for it to receive it.

What would be recommended for an area like Chicago where the temperature varies considerably?

Also, if the car is my DD and weekend warrior, should that affect which oil I choose?

Thanks!
Same question here :tup::)

Honestly 5w40 should be pretty nice, but you can do what I used to do when I run it though 3 seasons. 5w30 in the colder months, 5w40/10w40 in the hotter months. To avoid complications, keep your oil choices simple :)
 
#30 ·
Really appreciate you taking the time to do this. I will be a first time owner and have done a lot of reading including the STICKY's. I quickly learned to throw what "I thought" out the door. I have read that the oil filter you use can play a role in how your oil performs also. Might you add a few brands you and others may recommend from either personal experience or repidable data. My only question is when you either buy your Subie WRX/STI or when it arrives from ordering can you request the Subaru S Transmition fluid be put in when they do the checks? One other thing that I have gotten from reading is whatever oil you do chose to keep a quart of it in the trunk.
 
#31 ·
Nice information! How do u think of Motul x-clean? I'm a big fan of motul and I'm using it on my 15 sti now, it matches API SM rate which is manufacture's recommendation, but I've seen more people are using Motul Eco-nergy, its API SN, owner's manual says SN is the backup choice of oil, whats the difference?
 
#35 ·
The oil is great but the decision would have to be based on UOA which was pulled out of a boxer motor. German Castrol is superior to North American Castrol and hence why I'd recommend using it in our motors :)

Please make sure to check your oil every time you fill up! 3 minutes can save you lots of headache
 
#43 ·
"5w30 in the colder months, 5w40/10w40 in the hotter months. To avoid complications, keep your oil choices simple"

"Preferences would be under these following situations but you can't go wrong with 5w40 at anytime.
Colder weather = 5w40
Warm weather/summer time = 10w40

So 5W/40 would be more like all year around then?
 
#44 ·
"5w30 in the colder months, 5w40/10w40 in the hotter months. To avoid complications, keep your oil choices simple"



"Preferences would be under these following situations but you can't go wrong with 5w40 at anytime.

Colder weather = 5w40

Warm weather/summer time = 10w40



So 5W/40 would be more like all year around then?

Yeah, 5w40 can be used all year round, I live in the colder parts of canada and it works great, hot or cold.