I could not find any of the green German Castrol. All I could find was the gold. I found some made in 2005 and some made in 2006. They are both made in Germany however the bottles are a little different. The 2006 says European Formula on it. Has the gold changed its formulation from the 2005 to the 2006 batches? Has it been proven that the green is better than the gold? For the $6 price range is the gold german castrol the best option for synthetic oil? Thanks!