I have a friend who has owned a 2002 Toyota Echo since it was new; it now has approximately 115,000 miles on it. He has religiously changed the oil at 3,000 mile intervals and used Castrol GTX 5W-30. The car has developed a serious thirst for oil, and there are no apparent leaks. Is this car a known sludge issue? Any ideas as to why it would start rather suddenly using so much oil? I would think that 3,000 miles on a decent brand of oil in temperature moderate Portland, OR would keep an engine happy past 115,000 miles.