Signs that you need to change the synthetic motor oil of your vehicle include reaching the recommended mileage set by the synthetic oil manufacturer and difficulty starting up the engine in cold weather. Synthetic oil lasts longer than regular motor oil but costs two to four times more.
Mobil 1 Extended Performance synthetic oil lasts for 15,000 miles or one year, whichever comes first, lasting about five times longer than the typical 3,000-mile oil change that mechanics generally recommend. Royal Purple API-licensed synthetic engine oils let car owners drive for 12,000 miles.
Synthetic oils perform better under temperature extremes by not thinning under hot weather or maintaining flow during frigid temperatures. They are also resistant to breakdown and forming sludge which blocks the engine oil lines. When you have exceeded mileage recommendations and your car is slow to start, it is probably time to change the engine oil.