The only hope of an official spec sheet from Castrol is from an identical oil to GC Gold sold in other countries (England, South Africa, etc) where they do list decent spec sheets. Hard part is deciding if any of the possible oils are same as Gold GC sold in the U.S. Certainly at least one of them will be very close to Gold GC - SLX used to be but with recent changes in formulations, I'm not sure anymore. The info found on the sheets isn't all that useful anyway. If NOACK volatility was published, that would be another story. That's why I tested volatility myself since few oil makers want to give that info out.