5w40 in Subaru?

[Camprunner]

Today in WM I ran into a friend in the oil section and he was buying several quarts of Shell Rotella T synthetic 5w40 for his Subaru WRX I asked him doesn't your car recommend a 5 or 10w30? He said yes but he said many WRX guys like to run this?

Is this a common oil for Subaru WRX guys? Does the 4w40 show good UOA?

 

[CT8]

What would make the 40 a no go?

 

[Donald]

Rotella T is 15W40 non synthetic. Rotella T6 is 5W40 synthetic.

Despite what the "WRX guys" say about oil, I see no need not to follow whats in the owners manual . That assumes your driving a recent vehicle (not a 1960 Chevy wagon) and your not racing. Synthetic or non synthetic. My 2015 Forester calls for 0W20 synthetic. The WRX may get different oil, especially if a turbo.

Leave the Rotella oil for marine engines and diesel trucks.

I tried 5W40 in my Jeep and saw a small (1 or 2) MPG drop.

 

[skyactiv]

I owned a WRX and have posted a UOA on here of it. I'm not sure if one can really compare a 5W30 UOA one OCI to a 5W40 UOA another OCI and come up with an answer. The owners manual in my WRX stated a thicker oil might be necessary under certain conditions. Subaru listed odd weights however like 10W50 and one or two others I can't remember. What it boils down to is that the older WRX's didn't get good EPA numbers. My 07' with a five speed manual was rated 25 EPA highway. The STi and the WRX with an automatic was even worse at 23 EPA highway. That is knocking on gas guzzler tax territory and Subaru America had to recommend 5W30.

Older WRX's and WRX STi's really need to use a thicker VW 502 type oil to be safe.
Forget NOACK numbers for a minute. Many WRX 2.0 owners back in the day claimed high oil consumption when using Mobil1 5W30 and it going back to normal when switching to another brand.

 

[skyactiv]

Click on the photo to enlarge it.

 

[aquariuscsm]

I read this on an oil discussion somewhere on Yahoo last night:

*Diesel engine oils have a higher detergent (scrubbing agent) meaning it may remove deposits from the cylinder walls that actually help to seal the combustion gases. This could cause the engine to smoke & in turn damage the catalytic converter.*

Is this fact or fiction?

 

[Pablo]

XW-30, under heat and pressure provides marginal lower end protection for the 2.5L WRX and STI.

0W-40 for winter is great, and there really isn't a problem running a good synthetic 5W-50 in hot climates. Laugh, chortle, say what you want - but every WRX with a blown out bottom end, yep 5W-30.

 

[bullwinkle]

Originally Posted By: aquariuscsm
I read this on an oil discussion somewhere on Yahoo last night:

*Diesel engine oils have a higher detergent (scrubbing agent) meaning it may remove deposits from the cylinder walls that actually help to seal the combustion gases. This could cause the engine to smoke & in turn damage the catalytic converter.*

Is this fact or fiction?
Only if your engine has sludged up/worn out rings already-there are many fleets using the same dual rated HDEOs in gasoline & diesel engines. The cat damage occurs from engines that already burn oil, & even SN gasoline oil will eventually kill a converter.

 

[Merkava_4]

Originally Posted By: skyactiv
Click on the photo to enlarge it.


skyactiv, I see you're one of those weird people who put their Dock on the left side of the screen.

 

[CT8]

Originally Posted By: aquariuscsm
I read this on an oil discussion somewhere on Yahoo last night:

*Diesel engine oils have a higher detergent (scrubbing agent) meaning it may remove deposits from the cylinder walls that actually help to seal the combustion gases. This could cause the engine to smoke & in turn damage the catalytic converter.*

Is this fact or fiction?
It must be true if you read it somewhere. Cylinder wall deposits are killer and the detergents can scrub even the metal from the engine as well.

 

[jongies3]

I think they use it mainly because Subies burn through 5w-30 like tap water apparently. Considering how hard people push those WRX's and STI's around, I could see where a 40wt would be beneficial for high temperature, and abuse protection.

 

[bulwnkl]

My best results in my Subaru Baja (STi long block with a smaller-than-WRX turbo) was with RLI 5W40HD. Best in wear control, best in controlling/reducing consumption, and best in terms of mpg.

The EJ-25, in turbo form, frequently experiences a circumstance where it requires higher kinematic viscosity in order to provide sufficient oil pressure to the top end to keep decent flow going to the turbo. As Pablo mentioned, it also has a somewhat disturbing rate of coincidence of 5W30 & spun rod bearings.

I did not personally have good service with T6 in that Baja, but as I said, RLI's 5W40HD was absolutely brilliant.

 

[Padawan]

Yes, Rotella T6 5W-40 is quite popular among the WRX crowd, though I think the positive results are attributable more to the fact that it's an HDEO rather than to the brand itself.

I use various HDEOs in our 9-2X (rebadged WRX), and did the same in our previous Subarus. In warmer weather it's a 15W-40 and in colder months either a 5W-40 or occasionally a 10W-30.

 

[fozzdesy2001]

I have a 2004 Forester XT (turbo model, all stock) and have only used T-6 in it with a WIX or Denso filter changed every 5000 miles. It has 172 thousand miles so for me T-6 is good. I agree that the majority energy conserving 5-30 oils are just not enough in a 2.5 Subaru turbo engine or really any turbo engine for that matter. I also have a non-turbo Forester and would like to have one oil for both. These Subarus have both used T-6 but that is kind of overkill for the non-turbo one. What I would like to find is a 0-40 that will hold up in the XT. I have been thinking about trying Mobil 1 Euro formula 0-40 or Castrol Edge 0-40. Somewhere on BITOG I remember seeing a comparison of Mobil 1 and Castrol Edge but can not find it. Does anyone know how these two oils compare to T-6?

 

[dlundblad]

Originally Posted By: Camprunner
Today in WM I ran into a friend in the oil section and he was buying several quarts of Shell Rotella T synthetic 5w40 for his Subaru WRX I asked him doesn't your car recommend a 5 or 10w30? He said yes but he said many WRX guys like to run this?

Is this a common oil for Subaru WRX guys? Does the 4w40 show good UOA?


Back when I used FB more, a car guru friend from HS got into a debate with a bunch of Subi kids about oil.

A 5w40 isn't needed since its above 0°F.
A 5w40 is too thin for high heat.
A 10w40 was better for high temperatures. (Hopefully they at least used synthetic.)

I chimed in by giving them a link to BITOG.

 

[tojo1968]

Originally Posted By: jongies3
I think they use it mainly because Subies burn through 5w-30 like tap water apparently. Considering how hard people push those WRX's and STI's around, I could see where a 40wt would be beneficial for high temperature, and abuse protection.

It's hit or miss with Subaru. Some will use a qt/1k while others with the exact same model will not use a drop in 5k. My 06 Forester used the same amount no matter brand oil I used. 95% of the time I used M1 5w30. It used a half a qt/3k.
OP use what ever makes you comfortable. If you are in warranty, make sure you use an approved oil.

 

[Branson304]

Rotella T6 5W-40 is very commonly used in the WRX/STi community as well as other performance cars.

It's perfectly fine & the extra thickness helps in high performance applications I'm sure.

 

[FutureDoc]

Subarus have always (normally) been easy on oil (Save for some of the newer FB). Back with the old EJs, they would run anything without complaint. I used to run Shell T5 10w40 as well as QS Defy 5w20 without any complaint. Some FB25B sip the 0x20 some don't but most oil burners tend to stop if you up the weight unless there is a major mechanical issue.

As for the WRX, I think that the real reason Xw40 HDEO were adopted was part out of group-think culture along with the modification crowd seeking to alleviate self-induced stress on the engine. So you have a lot of folks turn to the HEDO to solve their poor/marginal engineering attempts, and then their thinking jumps to the greater WRX crowd. Most WRX UOA are not very good due to modifications having a negative impact... otherwise, stock WRXs UOA come back fine with the basic 5w30.

Personally, I am thinking about using T5 10w30 in my GC... mostly because the manual specs 10w30 and SM as acceptable for my Hyundai warranty.

 

[Gene K]

Another issue is fuel dilution on these engines. Especially when high boost rich aftermarket tunes are common. Add that to an engine that was likely designed to run a 3.5 HTHS oil and you see how a preshear predilued 3.1 HTHS ILSAC 5W30 could be marginal.

 

[CATERHAM]

The specified 5W-30 is certainly heavy enough even for spirited street use.
Most of the problems I've heard about have been attributed to oil starvation and a heavier oil isn't going to help much under those conditions.
My advice is to run the specified grade but keep the oil level at the maximum through out the OCI.
If you are doing something extreme such as tracking the car on a hot day then install an oil pressure gauge and preferably a oil temp' gauge as well.
If used correctly it will indicated if and when the car is prone to oil starvation, such as during hard cornering, and if the oil is getting too hot and therefore thin during sustained WOT conditions.