why wouldn't you trust it? the composition of oil breaks down and thats why it needs to be replaced every so often. The new oil does not break down as easily or as fast thus giving the same viscosity over a longer length of time. Sounds like an improvement on the synthetic to me. I'de say check with someone more knowledgeable about this and see how much it breaks down compared to the older one. Im sure Mobil is not going to sell a product that will allow you to not buy their product for 7500+ miles more that deteriorates your engine and makes them less money unless people see the new oil as being so good that they will only purchase that brand now.