Conventional oils that require changing at 3k miles are a petroleum based oil. When the viscosity and the shear wear protection are broke down over time and turn black from carbon build up.
Synthetic oils are just that...synthetic molecules is what makes up that type of motor oil .
Higher mileage vehicles are not recommended to make the full switch to synthetic in regards to possible preexisting leaks around rear main seal, valve covers, and other sites.
I recommend a 5w30 synthetic blend
〉 Answered on Nov 20th, 2010 by Amanda J. Pierce, MBA "AJ", Certified Mechanic, Project Coordinator; Primavera Scheduler at VIGOR Alaska Industrial Shipyard & BizzM3ch Solutions
Best to always consult your owners manual for the proper Oil Specifications:) Many of our clients have upgraded to Fully Synthetic Motor Oil for the benefits of convenience and better engine protection. Extended Oil change intervals will be more convenient for you and better for our environment. Good quality Synthetic Motor Oil will offer better protection for your engine, it is more stable at both cold and hot temperatures, it*s components reduce deposits and sludge build up that may cause engine wear.
More convenient, better for the environment, better for your engine. Good quality Fully Synthetic Oil is a win/win for you and your vehicle:)
Have a Fun Day!
〉 Answered on Nov 20th, 2010 by Diane Larson, Owner/Manager at Larson's Service