Q: My Honda Civic has a computer that estimates remaining oil life. That usually indicates I have about 50% oil life left when I reach the mileage indicated on my windshield sticker for my next oil change. The sticker is placed there by the repair shop doing the oil change. Should I follow the instructions of the manufacturer/car computer or the repair shop/windshield sticker? - Tim
A: Your Honda, like many vehicles, utilizes a sophisticated algorithm based on engine operating conditions such as speed, engine temperature, ambient temperature, and run-time in order to predict oil life. This provides a much more accurate estimate of oil condition than miles or time alone. I try to change my oil at perhaps 20% calculated life remaining, sometimes less. 50% is doing more to pump up the service provider's bottom line than to protect your engine!