I would also add that rubbing oil in fingers to confirm cleanliness is less than scientific. That extended performance oil is good, but may not have sufficient lubricity after 15K miles (determined by an actual procedure). Cleanliness also includes dirt in the micron size range (air filter to an extent), various metals, fuel, coolant, etc. Pay the $38 to have an analysis done. Going over 15K without the M1 filter rated for 15K is a fools gamble.