Mechanic put 10w50 in my Subaru

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May 9, 2020
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UK based here I’ve posted here before about Subaru engine oil....well I’ve just had my car serviced at one of the most respected Subaru engine builder/tuner in the UK and he put 10w50 in my Forester XT....the Subaru specialists in the UK here like RCM and Scoobyclinic don’t even sell or recommend lower than 10W50 or 10W40...so If anyone knows a thing or two about Subaru engines is going to be RCM...

Now my dad who is a very respected mechanic (does not live in the UK so he can’t service my car ) is absolutely adamant I need to drop the 10W50 and swap with 5W30/5W40 ASAP...he’s a bit old school stick to the manual kind of guy

Reading on about it at one point subaru factory fill in Japan was 10W50...any advice on this anyone also use 10W50 the specs for the oil are below....and the Subaru manual specs 5w30 up to 20w60 for severe environments/usage whatever that means....

Car is a 2008 EJ20 petrol turbo 230BHP 56k miles...
 

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Nice to see someone else on here from the UK!

Your 10w50 will be fine.

If it was mine I'd be running Shell Helix Ultra 5w40 as you can pick it up cheap and its a properly good oil. 2nd'd by Castrol Edge or Mobil1 FS 0w40 A3/B4.
 
Keep the oil and swap before winter for 5W40 then .... it’s an odd one that all the Subaru specialists and engine builders in the UK....all recommend minimum 10W40/50 and RCM 15W20 to the point they don’t even sell lower grades in their shops.....if anyone knows a thing or two about Subarus is going to be RCM...and they’ve been recommending the same for the last 10 15 years.....
 
Keep the oil and swap before winter for 5W40 then .... it’s an odd one that all the Subaru specialists and engine builders in the UK....all recommend minimum 10W40/50 and RCM 15W20 to the point they don’t even sell lower grades in their shops.....if anyone knows a thing or two about Subarus is going to be RCM...and they’ve been recommending the same for the last 10 15 years.....
What have you been running and how does she run with the 10w50? Notice any sluggishness off boost? Do you run the car hard? 240 BHP is high power density for a 2 litre.
 
10w50 is fine in that engine. esp if its not 0f outside.

thats a high hp per liter (energy density) application for a 2008 motor.

I'd prefer 5w40, but nothing wrong with 10w50 esp. going into summer.
 
Keep the oil and swap before winter for 5W40 then .... it’s an odd one that all the Subaru specialists and engine builders in the UK....all recommend minimum 10W40/50 and RCM 15W20 to the point they don’t even sell lower grades in their shops.....if anyone knows a thing or two about Subarus is going to be RCM...and they’ve been recommending the same for the last 10 15 years.....

A 10W* oil is good down to -20°c or so. Don't stress about it. Keep it in for your usual OCI, it'll be fine.
 
If the Forester tuned? monster turbo? intake'd/exhaust'd? modded to high heaven?
Do you monitor oil pressure or oil temperatures?

I see no problem with the 10w50 or mechanic.

Post a picture of the manual. I want to see the sheeple greenies whinecomplaincringe at the grades that you can use. In the collectivist USA, we only get the best MPG and least emissions grade single choice of oil. Choices is a thing of the past.

The photo is from the owners manual of a 2021 that the wife purchased here in the USA. I am pretty sure that this will be one of the last years of choices from this automaker. Most other non-exotic high volume consumer vehicles don't give choices. You will be assimilated and comply to thin oil one day too
 

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The car is stock , but will be re-mapped next month or so (still thinking if it’s safe to do so and worth it ).... I don’t monitor oil temp and on the motorway I do run it hard for the odd monthly motorway run...but normal driving the rest of time and no track days...
 
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If the Forester tuned? monster turbo? intake'd/exhaust'd? modded to high heaven?
Do you monitor oil pressure or oil temperatures?

I see no problem with the 10w50 or mechanic.

Post a picture of the manual. I want to see the sheeple greenies whinecomplaincringe at the grades that you can use. In the collectivist USA, we only get the best MPG and least emissions grade single choice of oil. Choices is a thing of the past.

The photo is from the owners manual of a 2021 that the wife purchased here in the USA. I am pretty sure that this will be one of the last years of choices from this automaker. Most other non-exotic high volume consumer vehicles don't give choices. You will be assimilated and comply to thin oil one day too
 

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The mechanic should have put in the normal spec'ed oil unless he discussed it with customer.
If what the OP indicated is accurate (not doubting it is), this oil viscosity is perfectly acceptable with Subaru. Sounds like this model is one of the few that lists multiple viscosities.

I see he just added snippets from the manual and I don't think any part of England falls under "high temperature" so it might not be ideal after all. Then again, the temperature range for all oils, including XX-50, is a lot broader than people think.
 
I just told him to put in what he thinks is best for the car this was after he’s done a full health check...he is one of the most respected Subaru mechanic and engine builder/tuner in the UK so I’m sure he’s done it for a reason and he knows what he’s doing....
 
....

Post a picture of the manual. I want to see the sheeple greenies whinecomplaincringe at the grades that you can use. In the collectivist USA, we only get the best MPG and least emissions grade single choice of oil. Choices is a thing of the past.

... You will be assimilated and comply to thin oil one day too
Good thing is any grade oil - 20, 30, 40, 50 - will still pour down that 710 fill hole.

Remember though, going lighter frees up HP and Torque - until the engine throws a rod
when you are going all RONIN on that Audi.

The trick is staying within the margins of safe area of operation
 
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