i BOUGHT A 2 LITRE FORD COURIER 15 YEARS AGO AND IT HAD A MAIN BEARING RUMBLE WHEN I STARTED THE MOTOR IN THE MORNINGS. I READ ABOUT THE DEVELOPMENT OF PS 23 AND BOUGHT A BOTTLE AND ADDED IT TO THE ENGINE OIL. TO MY SURPRISE THE RUMBLE DISAPPEARED AND NEVER RETURNED TO THIS VERY DAY.i NOW TREAT ALL OUR FAMILY CARS WITH PS 23