Hey Diesle Nut, just curious,who makes the recomondation for 15,000 between changes, is that from Amsoil itself or is that an independent study. I've always been of the understanding that It dosn't mater. that the oil should be changed at around the same intervals weather it be dyno. or synthetic, due to the soot build up in the diesel. Save a bit of money if thats the case---- I like that.