Buster,
The Mobil 1, 0w-30/5w-30/10w-30 don't meet the ACEA A3/B3/B4 tests - these are the most stringent test specs in the world for gas and diesel engine passenger cars. The Mobil 1, 0w-40 is thicker and hence meets these specs.
You can meet these specs with a 30wt synthetic, provided you formulate it towards the thicker end of the 30wt range, ie between 11.0-12.5 centistokes. This way it will also have a high temp/high shear viscosity of at least 3.5 centipoise and meet the ACEA specs ....
TooSlick