Hi. New to PSN and owning a diesel....2002 F250 7.3, 183,000. I found out the previous owner had replaced the turbo (stock) and head gskts...i'm figuring because of leaking on the gsks part...i now have a small amount of what appears to be oil foam on top of the coolant in the resorvoir...the coolant underneath this layer is clean, green, and no contamination......should i just flush the system and see if it cleans up, or ????? Also, should i run green af, and add the dc-8 or go to the gold where i don't need to add anything???? Thanks for any help, and am now an addict of the Blue Oval smokers!!!!!