Postby ShipFixer » Tue Apr 12, 2011 5:25 am
Smarty,
I've never seen Mobil 1 synthetic lose an independent test. That being said all the synthetics are pretty good for the average user.
If your spec calls for "diesel" oil stick with that. The real difference though is that they've kept higher amounts of molybdenum, zinc and phosphorus that used to be in all engine oils. They form a last line of defense that only really matters if you're seriously abusing an engine.
In the end though, if you go with a synthetic and change it regularly (thousand miles per quart of oil in the sump...acidity and contamination, not viscosity breakdown is really the driver) you'll be fine.