Green like any other oil or green like any other VW 508 00?
This. VW 508 00 isn't backwards compatible, so it has to be avoided to be run
in previous engines (calling for VW 502 00 or 504 00). That's why it's dyed.
It's most probably true that VWoA doesn't want the OP running VW 504 00 in
his 2021 GLI, but that isn't because it would harm that engine. It's just because
of CAFE. In a real world scenario they won't even notice as long as one does
additional oil changes as suggested (I said I'd change it right now and use an
OE filter).
.
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It most certainly is not. Where does it say that anywhere in your literature for your car?
The reason it is dyed is to prevent its use in a engine that requires a higher HT/HS than a 508 00 oil, not the other way around. Each time I have taken my new Tiguan into Volkswagen for the free oil changes I have requested they use 504 00 oil instead and they have done so without even asking why. A warranty is voided when the oil causes engine damage and there is zero possibility that a 504 00 oil will do so as compared to a 508 00.
This. VW 508 00 isn't backwards compatible, so it has to be avoided to be run
in previous engines (calling for VW 502 00 or 504 00). That's why it's dyed.
It's most probably true that VWoA doesn't want the OP running VW 504 00 in
his 2021 GLI, but that isn't because it would harm that engine. It's just because
of CAFE. In a real world scenario they won't even notice as long as one does
additional oil changes as suggested (I said I'd change it right now and use an
OE filter).
.
.