2019 Subaru WRX - No 0W-30 ?

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JS2000

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I just brought home a 2019 Subaru WRX. I live in Ontario Canada, while it is one of the warmer regions of our country it is plenty cold in winter and I will use my WRX all winter.

I was surprised to see that it has a 5w30 oil recommendation. I know it is a synthetic oil recommendation but I thought it might also have a 0w-30 recommendation for cold temp use, but it is not listed as an option. Subaru runs with a 6k mile oil change interval (10k kms) , no oil life monitor and they seem to buck the trend on 20 weight oils . Does anyone have any opinion on being able to run 0w30 oil on this engine (2.0 L DIT horizontally opposed) ? Thanks for any replies.
 
Originally Posted by JS2000

I just brought home a 2019 Subaru WRX. I live in Ontario Canada, while it is one of the warmer regions of our country it is plenty cold in winter and I will use my WRX all winter. I was surprised to see that it has a 5w30 oil recommendation. I know it is a synthetic oil recommendation but I thought it might also have a 0w-30 recommendation for cold temp use, but it is not listed as an option. Subaru runs with a 6k mile oil change interval (10k kms) , no oil life monitor and they seem to buck the trend on 20 weight oils . Does anyone have any opinion on being able to run 0w30 oil on this engine (2.0 L DIT horizontally opposed) ? Thanks for any replies.


IDK for sure but it may have something to do with the turbo. Can't see ny other reason.
 
?

Where has any mfg specified 0w-30 as a choice? I've never seen it. I'd be curious if anyone else has.

It is not a common viscosity found in stores.

Go ahead an use AFE; probably the only commonly available one around here @ least.
 
Maybe Subaru's had some bad experiences in the past.

Lesser 0W-30s can burn & shear their additional viscosity index improver (VII) enough to cause an operator-unrealised loss to the high-temperature high-shear (HTHS) properties, allowing a subsequent loss of film separating journals from bearings on spirited accelerations, followed by spun bearing damage.

Of course everyone has their own idea of what constitutes a lesser (or a not lesser) 0W-30 (ACEA A3/B4 rated? German vollesynthetisch rating?), and they simply wanted to avoid delving into that controversial fray. They may already be close to the borderline between acceptable CAFE mileage and full boost protection and they don't want their WRX owners to whittle that safety margin down unnecessarily. 5W-30 and 10W-30 use less VII than 0W-30, on average if the base oils are the same, but they're usually not the same either.

Save for the driving enthusiast who's also a tribologist/ engineer, it's gotten too confusing for a single paragraph in a dumbed-down owners manual (DD-OM).
 
"Lesser 0W-30s can burn & shear their additional viscosity index improver (VII) enough to cause an operator-unrealised loss to the high-temperature high-shear (HTHS) properties, allowing a subsequent loss of film separating journals from bearings on spirited accelerations, followed by spun bearing damage."





I would really like to hear some more reasoning behind this. Is it the 0?
 
I use 0W-40 in my FA20DIT

5W-30 synthetic is widely available and an easy viscosity to obtain. And Subaru is lazy with their chart. I honestly don't think it's any more complicated than that.
 
Thanks for all of the replies. Yeah I also wondered if they were being lazy with their chart, and I think their break-in procedures seemed outdated.

This is my first Subaru. I know with all of my other vehicles the owner's manual always had a couple of different oil recommendations based on ambient temps, you know the charts with the arrows on them, one single head arrow and one with a double head, etc..

After reading the replies I guess it is safer for them to recommend a 5w30 as it is easy to find everywhere, compared to a 0w-30. I just thought all 0w30's would be high quality synthetics with low VII's but I guess not. I don't want to risk any warranty issues so I'll stick with 5w30 and go with the best synthetic I can find. 0w40 sounds like a perfect viscosity to me , and maybe something I'd use out of warranty. Thanks for the replies.
 
Originally Posted by PimTac
"Lesser 0W-30s can burn & shear their additional viscosity index improver (VII) enough to cause an operator-unrealised loss to the high-temperature high-shear (HTHS) properties, allowing a subsequent loss of film separating journals from bearings on spirited accelerations, followed by spun bearing damage."





I would really like to hear some more reasoning behind this. Is it the 0?


I would really like to hear which 0W-30 oils are in the "lesser" catagory.
 
Originally Posted by simple_gifts
?

Where has any mfg specified 0w-30 as a choice? I've never seen it. I'd be curious if anyone else has.

It is not a common viscosity found in stores.

Go ahead an use AFE; probably the only commonly available one around here @ least.


GM has noted 0w-30 can be used in extremely cold climates in their manuals.
 
The most ordinary base oil starts out life as it's xW viscosity rating, and follows a Newtonian viscosity curve. To make it any "better" than a single weight viscosity oil, VII has to be added. So a SAE 0 oil can be made into a 0W-30 with enough VII.

Better finished oils use varying degrees of better base oils with their accompanying increase in natural viscosity index, and thus need less VII as the natural base oil viscosity increases. These are more heat and shear resistant.

The best base oil blends may have a high enough natural viscosity index rating that they can be made without any VII. These oils work well for racing applications.

If an oil has its VII damaged due to shearing or exposure to too much heat (continuous turbo usage?) it can lose some of it's HTHS. If HTHS started at 3.5 and operating conditions damaged it enough, that number could drop to 3.0 or less. There is some point where loss of HTHS may force parts into contact because the hydrodynamic film simply can't keep them separated. This is where having boundary layer lubrication becomes critical to avoid wear, but it too will eventually wear away from the contact surface and friction will rear its ugly head. After all, the AW content from lowering SAPS has progressively been reduced to extend the CATs lives, to stay in EPA compliance over time as your ICE ages.

There are also some arguments regarding the quality of the actual VII, the longer chain type is more prone to shear, the shorter chain is less.

I suspect Subaru does not want to have to declare that (for instance) Edge 0W-30 European formula is ok but AFE 0W-30 is not, because we all know formulas change, and what's reliable for a particular application this year may not be 2 years from now. They must see the 5W- and 10W- offerings as likely to remain reliable for their warranty period.
 
Originally Posted by "ammolab"
I would really like to hear which 0W-30 oils are in the "lesser" catagory. (sp)

Can't say - I'm speaking theoretically.
 
Originally Posted by CentAmDL650
The most ordinary base oil starts out life as it's xW viscosity rating, and follows a Newtonian viscosity curve. To make it any "better" than a single weight viscosity oil, VII has to be added. So a SAE 0 oil can be made into a 0W-30 with enough VII.


Not really. While base oil selection for the finished lube is certainly done while considering the intended Winter rating, there is no "SAE 0". Low viscosity base oils (4cSt, 6cSt, 8cSt) are blended to meet your typical 0W and 5W Winter ratings with the addition of PPD's, where necessary, to meet the CCS and MRV targets for that intended designation. If we were labelling those bases with SAE 100C viscosities you'd be looking at an SAE 8, SAE 16 and SAE 20 respectively.

A 6cSt PAO could be blended straight into a 0w-16 with no VII, or with a splash of VII to be a 0w-20. You could also blend the 6cSt PAO with an 8cSt PAO and produce a 0w-20 with no VII.

Reduction in HTHS is significantly less than the reduction in KV100, which is where mechanical shear of the VII polymers is most noticeable. Typically though, what many ascribe to shear, is often primarily the result of fuel dilution, if we are going by the UOA's we see on here.

Blending is of course a balancing act where final cost is a significantly consideration, ergo, one will typically find the cheapest bases necessary to meet the performance target(s). This means for your average 5W-xx, there will be little to no PAO used in a synthetic-labelled product, and perhaps a bit of Group III tossed in to keep the Noack down on your typical conventional. On the other hand, a 0w-40 or 0w-30 Euro lube with the 10% Noack ceiling will use PAO, sometimes in significant quantities, because you can use a heavier PAO due to its superior cold temperature performance, while benefiting from its inherently low volatility.

A "cheap" 5w-30 could be blended with a thinner base oil blend than a "premium" 0w-30, a subject which we recently explored in another thread. Looking at the volatility of the final product can be of value here.
 
Originally Posted by JS2000


After reading the replies I guess it is safer for them to recommend a 5w30 as it is easy to find everywhere, compared to a 0w-30. I just thought all 0w30's would be high quality synthetics with low VII's but I guess not. I don't want to risk any warranty issues so I'll stick with 5w30 and go with the best synthetic I can find.


I would give you the same recommendation for oil that I gave my son for his 2002 WRX, Pennzoil Platinum Euro L 5w30. Easy to find at Canadian Tire in 5L jugs and often goes on sale for around $32. It's a dexos2 oil, so it's going to have an HTHS of 3.5 or higher, providing that extra margin of protection compared to a typical dexos1 5w30 which will only be around 3.0 to 3.1.
 
I was formulating a reply, literally as Patman's post appeared. I'll just second what he said.
I would only add something, responding to part of your first post. Subaru is not just "bucking a trend" specifying 5w-30 instead of a Xw-20. This is clearly one of those high-stress, high-temp applications where I'd want every bit of the higher HTHS that comes with dexos-2 (even if that isn't explicitly required by Subaru). I'm totally comfortable with 20wt in my Prius, and might even try it in the Avalon per the back-spec, but with your car, particularly in wty, I'd actively stay as close to the center of "the envelope" as I could. There's real potential for things to go really wrong if you go one step too far while playing amateur test pilot. . .
 
Last edited:
There is a Shell/Pennzoil 0w30 that conforms to the VW504.00 specification - if you really want a 0w30 use that, since it is developed for DI turbo long drain applications. It's one of very few 0w30s to conform to this very demanding specification where most are 5w30. Personally I'd stick to 5w (and probably still use a 504 approved oil) but it's your car! Happy motoring
smile.gif
 
I have ran M! 0-40 in my WRX before but for most of its life Valvoline 5W-30. I have in the stash some PP Euro-L that will be going in on the next change.
 
Originally Posted by Patman
Originally Posted by JS2000


After reading the replies I guess it is safer for them to recommend a 5w30 as it is easy to find everywhere, compared to a 0w-30. I just thought all 0w30's would be high quality synthetics with low VII's but I guess not. I don't want to risk any warranty issues so I'll stick with 5w30 and go with the best synthetic I can find.


I would give you the same recommendation for oil that I gave my son for his 2002 WRX, Pennzoil Platinum Euro L 5w30. Easy to find at Canadian Tire in 5L jugs and often goes on sale for around $32. It's a dexos2 oil, so it's going to have an HTHS of 3.5 or higher, providing that extra margin of protection compared to a typical dexos1 5w30 which will only be around 3.0 to 3.1.


Thanks that sounds like a great recommendation, easy to find and relatively affordable, and what sounds to be a high quality fit for my car. Thanks for the reply
 
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