I am wondering if anyone knows what the definition of "extended drain" means exactly? It used to be that auto manufacturers recommended 3000 mile drains, then 4000 mile drains and now some are recommending 7500 mile drains. I assume that these increasing drain intervals from the manufacturers are not what they consider "extended drains", but they may have been before they implemented them. I hear that in Europe, 20,000 mile drains are normal in some cars there -- is that extended drains? Any thoughts people? Thanks in advance.