B in B,
The Ford rep did not say, but it is generally regarded in the engine world that rings wear-in better with a petroleum based
oil. It's not as "slippery" as
synthetic. Of course, there are many variables to this, depending on how the engine was set up. But for most, break-in should be with NON
synthetic oil. If the rings don't seal properly,
oil consumption could be an issue, especially as the miles add up.
All Mobil 1 oils are 100%
synthetic. Don't confuse Mobil 1 with the regular Mobil oil, which is petroleum based. The multi viscosity helps maintain oil performance in a wide range of temperatures. Most of us deal with anything from around 30 degrees, to over 100. Pretty hard to get a single weight oil to be happy in that! Of course, once the engine is at N.O.T., the oil would be functioning at it's heaviest rating. Also, synthetics virtually never wear out, like a regular oil, but it does get contaminated. This is why the longer change interval. OEM's that do lots of highway miles, it's not uncommon to get 25,000 miles on a change, with synthetics.
Bottom line: ALL modern oils are pretty good. Match the weight and grade to your engine, environment, and driving style.
Dave
