Unlike what many mechanics might tell you in car dealerships and service stations, synthetic oils can go quite the distance. Here’s what some of the worlds leading brands have to say: Mobil 1 Extended Performance synthetic oil is recommended for oil change intervals up to 15,000 miles or one year, whichever occurs first. Royal Purple API-licensed synthetic engine oils allow motorists to travel as many as 12,000 miles as the recommended oil change interval. Even more amazing, Royal Purple HPS synthetic performance upgrade street oils allow up to 15,000 miles in between motor oil changes.