I just noticed that AMSOIL website does not suggest using their european formula for extended Oil change! why is that?
From AMSOIL page
"Service Life
Use drain intervals according to the manufacturers' recommendations for synthetic motor oil."
They can't. Each Euro. manuf. has their own OCI in addition to the fact that it's different for each vehicle/driver/driving pattern/conditions ie. flexible mileage OCI service intervals...
eg. my friends' `04 M-B C240 initially said 10k mi. up until about 5k...and then when it figured out that the car sat for 6 mo. at a time, it said "service car now" within a couple days of the 6k mi. point...