Most automobile manuals state that synthetic motor oil should be changed every 7,500 miles under normal driving conditions, which is about 2.5 times longer than conventional oil. Auto mechanics will commonly counsel drivers to adhere to the mileage recommendations in their manuals, but they still advise changing the oil at least once a year at the minimum regardless of the mileage.

On the Other: Not All Are Created Equal

Finding common ground on this subject has become more elusive due to the increase in high-performance synthetic oils on the market. Some of these oils claim to last anywhere from 15,000 to 25,000 miles before any chemical breakdown takes place. Therefore, proponents of these newer synthetics argue that the commonly accepted 7,500-mile interval should be re-evaluated.

Bottom Line

The best bet is to always follow the mileage recommendations in your automobile owner's manual. As engine and synthetic oil performance increase, change intervals listed in these manuals will likely change or increase through time. Those visits to get your oil changed also help alert drivers to other potential problems they might otherwise be unaware of. Safety is key. Consult with a trusted mechanic first if you plan to extend the change interval beyond what is in the manual.

Source:

Trust My Mechanic

OmniNerd.com

Amsoil Ultimate Performance

Resource:

Chemical and Engineering News: Motor Oil