OK I have used Mobil 1 from the get go(new) with two vehicles and outside of it not leaving sludge on the heads and valves...I saw no difference. I did 5K oil changes with the Mobil1 and my 01 Saturn started burning oil at 80K. The added protection the synthetic provided was not visible to me or worth it. Maybe in performance motors like the Vette or North Star engines.
I am a firm believer in: if you stay on your oil, use a good filter(prime it with oil before installing it), don't push the oil beyond the 3-4500k mark and the motor will serve you well in the compression dept. Wally World oil is fine, so is Pennzoil and Quaker State. Whatever is on sale. But in my dirt bikes and 4 wheelers I use Castrol GTX. I buy filters in bulk on E Bay for all my vehicles.
We recycle the oil and filters here in my town. So that makes it easy to do your own.