||Eventho a synthetic oil may be rated the same viscosity of a ||conventional oil. I've heard that the synthetics contain smaller ||molecules than that of a conventional oil.
As I understand it, it's more the case that a synthetic has all identical molecules, chains the same length. Conventional oil has a range of sizes, so the weight is more of an average for that batch.
||Since the molecules are smaller they say that if you have any oil ||leaks that they will probably leak faster.
Early Mobil 1 formulations had a lower surface tension, which meant they leaked easily. That formula changed long ago, plus engines are much better sealed now. Today it's a non-issue.
||I wrote to Shell about using their Rotella Oil in my diesel tractor. || ||Their response was "Use any of our Multi-grade Convention oil, because ||it doesn't get cold enough in North Carolina to see a benefit from ||using our Synthetic versions."
Good for them! Texas Parts Guy