My engine uses one quart of oil every 250 miles. It has 175000 miles on it. Sparkplugs do not have black deposits on them. Compression appears to be good. Valves were checked by mechenic and seals were replaced. PCV system was removed and cleaned. There doesn't appear to be any major leaks. There is an oily film at the exhaust pipe. Do you think it is possible that there are cracks in the head that would allow the oil to get into the exhaust manifold wihout getting into the cylinder block?

My engine uses one quart of oil every 250 miles. It has 175000 miles on it. Sparkplugs do not have black deposits on them. Compression appears to be good. Valves were checked by mechenic and seals were replaced. PCV system was removed and cleaned. There doesn't appear to be any major leaks. There is an oily film at the exhaust pipe. Do you think it is possible that there are cracks in the head that would allow the oil to get into the exhaust manifold wihout getting into the cylinder block??
No, the problem is the piston rings, it's burning a little oil only while running and not enough to see any actuall oil on the plugs and not enough to make it smoke, I'd say just let it be. Otherwise you're talking rebuild or replace the engine, it'll probably run another 100.000 miles like that (slightly exaggerated but you get the point) don't be alarmed.