I STARTED USING THE HEAVY DUTY OIL STABILIZER AT 105,000 MILES AND NOTICED THE CART RUNNING QUIETER RIGHT AWAY! IT SEEMED TO PROGRESSIVELY MAKE THE CAR RUN EVEN BETTER AS TIME CONTINUED ON. I USE 1 AND A HALF QUART WITH EACH OIL CHANGE. AT 235,000 MILES, THE ENGINE HAS AS MUCH POWER AS IT DID WHEN NEW, AND IT RUNS COOLER WITH ABOUT 1 MPG BETTER GAS MILEAGE! NOW WHEN I CHANGE MY OIL, IT LOOKS ALMOST AS CLEAN AS WHEN I PUT IT IN!