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Discussion Starter · #1 ·
Hi friends,

Possibly a dumb question (as I for some reason cannot fully wrap my head around the oil viscosity thingy), but my 2013 2.5 Prem CVT manual recommends 0W20 synthetic oil. If I was to use Mobil 1's 0W40 oil instead, would it do any harm, either in short run and/or over time?

I currently have only a few hundred miles on my 2013 OB, but plan on doing first new car oil/filter change around 1000 mile mark.

thanks,
plex :cool:
 

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Meh.
I has wagons.
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12,382 Posts
That is MUCH thicker than what it calls for.

I would not use it.
 

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2011 Outback 3.6 Premium
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721 Posts
I would use the viscosity specified in the owners manual. 0w40 is MUCH heavier than 0w20. Using it, even once, can do serious damage to your engine if it's spec'd for 0w20.
 

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2011 Outback Premium 6MT
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546 Posts
Hi friends,

Possibly a dumb question (as I for some reason cannot fully wrap my head around the oil viscosity thingy), but my 2013 2.5 Prem CVT manual recommends 0W20 synthetic oil. If I was to use Mobil 1's 0W40 oil instead, would it do any harm, either in short run and/or over time?

I currently have only a few hundred miles on my 2013 OB, but plan on doing first new car oil/filter change around 1000 mile mark.

thanks,
plex :cool:
you are much better off buying the OEM Subaru oil and filters (at least until the warranty is up) This will give you more legs to stand on if there is ever a mechanical problem with the engine during the warranty period. Also, keep your receipts.
 

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05 OBXT 5eat stg1.2
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To oversimplify, the first number is cold viscosity (start up or severe cold). The second number is hot viscosity (operating temp). If the recommendation is 0w20, then you can substitute anything with the last number of 20. You could also do a 30 if you felt like it. But a 40 is diesel and high temp territory. No need for that. It wouldn't hurt anything other than your mpg, but there's no reason to do it unless you were driving through the desert uphill.

Reasonable substitutes for 0w20 would be a 5w20, 0w30, or 5w30. Anything over that would be pointless. The only reason they recommend 0w20 over the previous 5w30 is efficiency. It is simply to help with gas mileage.
 

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Meh.
I has wagons.
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12,382 Posts
To be fair, the FB series engine has been 0w20 from the get go, it isn't a back spec type deal.
 

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2016 Outback 2.5i Premium w/nav/eye
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366 Posts
To oversimplify, the first number is cold viscosity (start up or severe cold). The second number is hot viscosity (operating temp). If the recommendation is 0w20, then you can substitute anything with the last number of 20. You could also do a 30 if you felt like it. But a 40 is diesel and high temp territory. No need for that. It wouldn't hurt anything other than your mpg, but there's no reason to do it unless you were driving through the desert uphill.

Reasonable substitutes for 0w20 would be a 5w20, 0w30, or 5w30. Anything over that would be pointless. The only reason they recommend 0w20 over the previous 5w30 is efficiency. It is simply to help with gas mileage.
" The only reason they recommend 0w20 over the previous 5w30 is efficiency. It is simply to help with gas mileage. "

better known as C.A.F.E.<!-- / message -->
 

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Discussion Starter · #8 · (Edited)
Hi all,

Thanks for all your replies. I think the consensus is to stick with the recommended 0W20 and also, as RobMunach mentions, stick with Subaru brand 0w20 oil and filter, at least during warranty in case of any hick-ups with the engine down the road.

Reason why the 0W20 vs 0W40 conundrum came up is that my 07 Saab 93 2.0T is due for an oil change soon, and I was shopping for 0W40 for the Saab, so was thinking of just getting same oil for OB while I'm at it, but I guess its better to stick with manufacturer recommendation (0W20).

Again, thanks for all your inputs! :)

Cheers!
plex :)
 

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Meh.
I has wagons.
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12,382 Posts
Any 0w20 that meets API SM or SN specs will be fine. Dealer oil can be very expensive.
 

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2010 OB 3.6R limited
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3,284 Posts
hi friends,

possibly a dumb question (as i for some reason cannot fully wrap my head around the oil viscosity thingy), but my 2013 2.5 prem cvt manual recommends 0w20 synthetic oil. If i was to use mobil 1's 0w40 oil instead, would it do any harm, either in short run and/or over time?

Thanks,
plex :cool:
do not use 0w40
 

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2017 Outback, 14 Jeep Grand Cherokee, 07 BMW E-93
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Using 0-40W will do no harm what so ever to your engine. It will just cause the engine oil pump to pump harder than it needs to which is a mechanical loss meaning you are making your engine run slightly harder than it needs to resulting in a minor loss in mpg.
That is why most manufacturers have spec'ed this oil it flows better.

Even my BMW E93 twin turbo engine spec'ed 5-30W which certainly runs hotter off the turbo discharge than the Subaru normally aspirated engines do.

What oil does the Forester turbo run, anybody know? I am guessing a little thicker than the 20 weight...
 

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Meh.
I has wagons.
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2011 Outback Premium 6MT
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Using 0-40W will do no harm what so ever to your engine. It will just cause the engine oil pump to pump harder than it needs to which is a mechanical loss meaning you are making your engine run slightly harder than it needs to resulting in a minor loss in mpg.
That is why most manufacturers have spec'ed this oil it flows better.

Even my BMW E93 twin turbo engine spec'ed 5-30W which certainly runs hotter off the turbo discharge than the Subaru normally aspirated engines do.

What oil does the Forester turbo run, anybody know? I am guessing a little thicker than the 20 weight...
I think there is more to it than just the pump having to work harder. It can only work so hard before the relief valve opens up. The oil galleries and bearing clearances may be smaller in this engine due to the lower viscosity oil. Some areas may not get sufficient quantities of oil. Why take a chance? T
 

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2011 OB 2.5i Prem CVT HK/AWP, Ruby Red Pearl
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I think there is more to it than just the pump having to work harder. It can only work so hard before the relief valve opens up. The oil galleries and bearing clearances may be smaller in this engine due to the lower viscosity oil. Some areas may not get sufficient quantities of oil. Why take a chance? T
I would like to think engine designers consider that at some eventual point – oil gets dirty (and is there forever).<O:p</O:p
<O:p</O:p
Mobil 1 0W-40 Viscosity Index 185 / Mobil 1 0W-20 Viscosity Index 173.<O:p</O:p
Chemically, both oils exceed Very High VI (>110) classification. Mechanically, I doubt the 0-40 would fail lubricity performance, correlating the Forester-T runs Syn/5-30. Insert-Make-Here run 0-20 to hit better 40ºC/100ºC ASTM specs, CAFE as alluded to.<O:p</O:p
In (practical) application, it makes no (oil related probability) difference whether in–warranty/off-warranty, you either run spec/non-spec – get the 0-20 (especially if you DIY).
 

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2010 OB 3.6R limited
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if Subaru spec'd our 0W20, why would you want to use 0W40?
Unless you have a 55 gallons of 0W40 oil sitting in your garage!! I just think is borderline comical that you even think abt using 0W40.....

Better yet, Maybe you should prove us all wrong, Test it our on YOUR BRAND NEW $30K SUbaru..... Let us know how the car run with this 0W40 oil....:):)
 

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Ok so the 0w-40 thing don't do it but also don't change your oil at 1k. Its a waste and the new oil has break in additives. If you want to change it early wait till 3k.
 
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