Castrol EDGE Euro is also VW 508 spec.
The mechanic is absolutely wrong. You must use a 5W-40 C3 oil with the Fiat 9.55535-S2 specification, I use the Castrol Magnatec 5W-40 C3, which is cheap and easy to find, but any other brand with the correct specification is fine. A 0W-20 oil has insufficient pressure and film strength, and will lead to damage over time.
I have a 450k km 1.9 tdi, and a 300k km 1.6 tdi, i always use 5w30 castrol, no issue.
My mom's impreza will loose oil between oil changes with 0w-20 and will be fine with 5w-30. It burns the thinner oil.
My wife\u2019s 2012 Impreza is at 195k miles and I switched it to 0w-30 and then 5w-30 due to oil consumption. Was burning a quart every 1K miles on 0w-20, burns half that on 5w-30. I\u2019m actually considering going thicker.
The dealership here itself was using 5w-30 as the default for oil changes even though 0w-20 is stamped on the filler cap. After checking myself that Subaru said that would be OK, I started using it too for my own changes just to avoid flipping back and forth -- though I have no idea if that would be a problem. In any case, the Forester seems happy, even if the mileage may have dipped slightly.
Engine does become a bit quieter with 5w-30.
I would only suggest using \"premium\" oil brands, like Castrol or Elf, in correct specification.
Castrol is fine
It\u2019ll be okay. Subaru engines are robust and that mix rate won\u2019t increase the viscosity enough to affect the oil flow rate out to the cams.\nPardon my skepticism regarding Castrol oils though. Haven\u2019t been a fan of them since the GTX days. The additives they\u2019d chuck in their generically sourced base oils glazed bores and gummed lifters.\nCost many a machine shop like ours a fortune in comeback work.
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If choosing engine oil across many manufacturers, check the part ranking. If your choice is down to two brands, the PartReview part comparisons help.
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In March 2026 on PartReview, engine oil Castrol were overall better than OEM Subaru.
In March 2026 on PartReview, engine oil Castrol were overall more popular than OEM Subaru.
By vote balance, engine oil Castrol surpassed OEM Subaru:
By number of reviews, engine oil Castrol surpassed OEM Subaru:
In March 2026, according to PartReview, engine oil Castrol led more car-specific ratings than OEM Subaru:
Castrol are chosen by owners of cars such as: Skoda Octavia, Audi A6, Audi A7, Audi TT RS, Ford Explorer, Volkswagen Beetle, Volkswagen Corrado, and others.
OEM Subaru are chosen by owners of cars such as: Subaru Forester, Subaru Impreza, and others.
If this comparison didn’t fully answer your question, there are many others on PartReview.
For example, comparisons of engine oil Castrol with: Mobil, LIQUI MOLY, MOTUL, Shell, AMSOIL, VALVOLINE, PENNZOIL, RED LINE, OEM Toyota, Mannol.
Also available: comparisons of engine oil OEM Subaru with: Mobil, LIQUI MOLY, MOTUL, Shell, AMSOIL, VALVOLINE, PENNZOIL, RED LINE, OEM Toyota, Mannol.
You can also see who is better among other engine oil manufacturers: Mobil or Castrol, Mobil or LIQUI MOLY, Mobil or MOTUL, Mobil or Shell, LIQUI MOLY or Castrol.
