[stephen]

Perhaps I can offer some insight as a chemist.

From what I can find on the internet, conventional oil base stock is a complex mixture of organic molecules, including aliphatic and aromatic hydrocarbons. To this is added a lot of other things including detergents, viscosity additives etc.

Synthetic oil is also hydrocarbon based, it's just that it's a mixture of fewer specific molecules. It contains pretty much the same additives as conventional oil. It may be that by selecting exactly what goes in it that the properties can be somewhat optimized.

However, the two are very similar, a mixture of various hydrocarbons and additives.

[shadow5403]

Either way, you need to properly change your oil. Yeah synthetic will hold up longer...but you should still at least change the oil filter and check the level and add a quart if need be if yur gonna go over 5k without a change.