Minivan 4 cyl with 185,000miles is losing 1 1/4 quarts oil per week. Head gasket was changed 2 months ago. How do I tell if plastic valve seals in head under the springs are leaking by , or the bottom oil rings on the pistons are wore out. Engine smokes during warmup only, and I see no oil leaks underneath. russwr@hotmail.com
(NO, I'm not oiling up the highway)

If you get blue smoke during warm up it is probably the valve seals going bad. Common problem on high mileage cars. Try a can of Restore in the oil at the next oil change. If the rings are going bad this may help the oil burning problem if it is the rings. My money is on the valve seals though.