I do not go by milage at all just time in service in terms of months. I have done a few 9 month oil changes before but I generaly keep them to 6 months but my vechile also generates a lot of insolubles especialy dureing the winter months so for me milage is never an issue and wear is not either it is always a concern about the insolubles. The only way around this would be to change the filter at 6 months and see if that helped. Better yet go with a bypass filter system. That is the only real thing stoping me from doing 12 month OCI! I plan on driveing my Camry until the wheels fall off and Ihave to pay a salvage yard to take it off my hands so for me cleanliness is faramount. The retail price for dino keeps going up at a faster pace then the synthetic so preety soon their is not going to be more then a $1 difference at the retail level.