I've used Blucol for years. Makes no difference to the cooling system what so ever. It's listed as suitable in the service manual. . Oat is only specified to meet anti pollution regulations.
It doesn't need to be changed so often which is why it's used, ie less changes = less pollution.
I use Blucol because I've 30 gallons in Stock. Once I've run out I'll use Oat.
Doesn't OAT have specific anti corrosion properties?