97 HX 5spd 225k stock. The car is turning the oil black in 500 miles and then the engine sound like it is lacking lubrication and metal on metal sounds valve noise etc. If I change the oil it sounds fine for the next 500 miles. Car is still getting 42mpg and running very strong. Compression is 175, 175, 165, 175. Pcv is new, Egr has been cleaned, full ign tuneup, timing is on, valves have ben adjusted, plugs are nice and white. I am assuming fuel is diluting the oil but I can not see how considering the compression is good and my mpg is good. I guess it could be a valve seal, I have not performed a leakdown test since I dont have the tool. I am hoping you guys have an idea. If i need to rent a leakdown tester I will.