I think sometimes a motor gets used to one oil and changing it might upset the apple cart, so to speak. However, I recently changed the oil in my '84 Ford and went to Mobil I because I was going to Atlanta and wanted to see if I could squeeze out a few more MPG at $4 per gallon at the time. Now I am committed for life to using synthetic in it, but I did get better MPG with it on the trip, so maybe it was a wise choice.

In my T I run Rotella T because I have heard so many good things about it.

Don