I put about 1500 miles on my car when it just started getting oil in the cooling system. I did the head job, and it took about 20,000mi to finally get the system clean. I did two flushes, new radiator, new hoses, new expansion tank, and constantly wiped out the excess oil from the expansion reservoir every month or so. It takes a long time....I was quite concerned as well. But the coolant has been spotless clean for the last year or so.