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.
I would only suggest using \"premium\" oil brands, like Castrol or Elf, in correct specification.
Castrol Power1 is really good though
I change the oil myself...to ensure it's done correctly and with quality oil (I use Castrol Edge). And I go by the oil minder. I do smell gas during oil changes but it's not strong and never in the cabin between oil changes as some have reported.
I have a 2010 civic si, I use shell rotella T-6 5w-40 due to burning issues and one quart of Castrol 5w-30 high mileage full synthetic (I’m picky lol- but my car runs smooth and has consistent oil levels on the dipstick through the weeks after oil change)
Buy Castrol Edge engine oil for your Mazda 2.5, but do get the Mazda transmission oil.
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.
We compare engine oil across these categories:
In March 2026 on PartReview, engine oil Castrol were overall better than RED LINE.
In March 2026 on PartReview, engine oil Castrol were overall more popular than RED LINE.
By vote balance, engine oil Castrol surpassed RED LINE:
By number of reviews, engine oil Castrol surpassed RED LINE:
In March 2026, according to PartReview, engine oil Castrol led more car-specific ratings than RED LINE:
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.
RED LINE are chosen by owners of cars such as: Audi S3, 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, OEM Toyota, Mannol, RAVENOL.
Also available: comparisons of engine oil RED LINE with: Mobil, LIQUI MOLY, MOTUL, Shell, AMSOIL, VALVOLINE, PENNZOIL, OEM Toyota, Mannol, RAVENOL.
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.
