Rotella T6 5W-40 for Subaru WRX STI

[The Critic]

A family friend asks me to do an oil service on his 2004 STI. Despite my dislike for these cars, I agreed. He specifically requested that I use Rotella T6 5W-40 in the car. I recognize that the car calls for 5W-30 but it seems like WRX/STI owners tend to prefer a higher-viscosity oil, even if they do not track or drive the car hard. And Rotella commonly comes up as the oil of choice.

So, what's the big deal about using Rotella T6 5W-40 in these cars?

 

[LazyDog]

I have a Volvo Turbo that been using the 5-40 Rotella and it seems to like it!

 

[FA_WRX]

Originally Posted by The Critic


So, what's the big deal about using Rotella T6 5W-40 in these cars?



Rotella T-6 seems to have earned a large Subaru following for it excellent UOAs when used in The EJ platform.

 

[A_Harman]

Originally Posted by The Critic
A family friend asks me to do an oil service on his 2004 STI. Despite my dislike for these cars, I agreed. He specifically requested that I use Rotella T6 5W-40 in the car. I recognize that the car calls for 5W-30 but it seems like WRX/STI owners tend to prefer a higher-viscosity oil, even if they do not track or drive the car hard. And Rotella commonly comes up as the oil of choice.

So, what's the big deal about using Rotella T6 5W-40 in these cars?


I think it's because RT6 is the cheapest synthetic 5w40 that is readily available in the local Walmart, and is used in turbocharged engines.
Problem is, those turbocharged engines are diesels.
I think there are better 5w40 synthetics out there that are formulated specifically for turbocharged gasoline engines.

 

[The Critic]

Originally Posted by A_Harman
Originally Posted by The Critic
A family friend asks me to do an oil service on his 2004 STI. Despite my dislike for these cars, I agreed. He specifically requested that I use Rotella T6 5W-40 in the car. I recognize that the car calls for 5W-30 but it seems like WRX/STI owners tend to prefer a higher-viscosity oil, even if they do not track or drive the car hard. And Rotella commonly comes up as the oil of choice.

So, what's the big deal about using Rotella T6 5W-40 in these cars?


I think it's because RT6 is the cheapest synthetic 5w40 that is readily available in the local Walmart, and is used in turbocharged engines.
Problem is, those turbocharged engines are diesels.
I think there are better 5w40 synthetics out there that are formulated specifically for turbocharged gasoline engines.

That makes sense. Any particular recommendations?

 

[SubLGT]

Originally Posted by The Critic
...So, what's the big deal about using Rotella T6 5W-40 in these cars?


You can find a very lengthy answer here:
https://forums.nasioc.com/forums/showthread.php?t=2714154

An excerpt:
Quote
...Subaru introduced the turbo EJ engine in the 1991 Legacy turbo, and began selling them in volume with the 2002 WRX. The engine's lone remaining application is in the 2015+ WRX STI. This engine is the most problematic Subaru engine for oil selection because of the sub-optimal recommendations made by Subaru (particularly after 2010) combined with aggressive tuning of the engines for fuel economy and emissions. A full explanation of the issues is beyond this guide, but the primary issue is spun bearings due to contact between the crankshaft and the bearing (lubrication failure) the proximate cause is detonation which can be worsened by oil ingested through the PCV. Additionally oil which is thin either because it's very hot or because of poor shear stability is less capable of protecting the bearings. It is therefore reasonable to use a thicker oil in a turbo EJ to reduce, but not eliminate, the chance of a spun bearing.

Street Driving
The Resource Conserving 5w30 recommended in the owner's manual (synthetic from 2011) is just barely adequate for street driving, especially in the 2008-2014 WRX which does not have an oil cooler. A quality, shear-stable RC 30 grade synthetic conforming to ACEA A5/B5 specifications is recommended as a minimum. Heavy Duty 30 and 40 grade oils are a reasonable upgrade.

Heavy Use
Turbo EJ owners who use their car heavily are wise to use a HD 30 grade oil at a minimum, and HD 40 grade oils can provide additional safety margin. Installation of an oil cooler in cars not so equipped from the factory is wise for heavy use, a high capacity aftermarket cooler can provide additional safety margin.

Modified Engines
Owners of modified cars are wise to use Heavy Duty 30 grade oil at a minimum for street use. Modified cars receiving heavy use should have an oil cooler installed in addition to the use of HD oil. For occasional heavy use, modified cars can get away with shear stable HD 40 grade or 50 grade oil conforming to ACEA A3/B4, or a combination of E7 or E9 and a gasoline specification like API SM...

 

[A_Harman]

Originally Posted by The Critic
Originally Posted by A_Harman
Originally Posted by The Critic
A family friend asks me to do an oil service on his 2004 STI. Despite my dislike for these cars, I agreed. He specifically requested that I use Rotella T6 5W-40 in the car. I recognize that the car calls for 5W-30 but it seems like WRX/STI owners tend to prefer a higher-viscosity oil, even if they do not track or drive the car hard. And Rotella commonly comes up as the oil of choice.

So, what's the big deal about using Rotella T6 5W-40 in these cars?


I think it's because RT6 is the cheapest synthetic 5w40 that is readily available in the local Walmart, and is used in turbocharged engines.
Problem is, those turbocharged engines are diesels.
I think there are better 5w40 synthetics out there that are formulated specifically for turbocharged gasoline engines.

That makes sense. Any particular recommendations?


M1 Formula M
Pennzoil Platinum Euro
Valvoline MST or HST

If you want to get more boutique, Joe Gibbs Driven DT40