Signature A4 is currently using a quart of oil every 400-500 miles. Mileage is now 140k. Rebuilding the engine is $7k, so adding oil is inconvenient but relatively cheap. Will the continued blow-by of oil lead to problems with the turbo or exhaust system? I intend to keep the car because it is dent and rust free and everything works (plus I detest the shut-off feature on the newer A4s).