One thing that makes Euro oils different from oils for American and Japanese engines is HT/HS and viscosity. 0w30 oils for American and Japanese engines have a lower HT/HS than 0w30 Euro specification oils. Castrol Euro has at least a 3.5 HT/HS, other 0w30 oils have about 3.1 HT/HS or less.
Another difference is additive packs. In some cases, an higher SAPS level is allowed when compared to SM/SN engine oils which are a Xw30 viscosity.
Another difference is additive packs. In some cases, an higher SAPS level is allowed when compared to SM/SN engine oils which are a Xw30 viscosity.