My 05 WRX now has 192,000 miles (bought it new with 7) and I have been running Valvoline Max Life Synthetic Blend (5w-30winter 10w-30 summer) for the past 50,000 miles or so. Recently my car has been loosing oil between changes. It has been for a little while now, but it seems more than usual. Not sure if its the engine or possibly the liquid gasket on the oil pan. Either way i am going through 1.5-2 quarts every 3500-4000 miles.
First Question: I was always told when you switch to High Mileage Oil, never switch back. Not sure the reason why, but is this true?
Second Question: Will this increase my potential leakage by switching away from High Mileage and to Full Synthetic?
Third Question: Should I move up in viscosity (High Mileage Blend or Synthetic)10w-40?