An interesting idea. I hadn't done it because there are those who are MUCH more knowlegable than me about oil on bob is the oil guy and the like, but I could add some personal experience about from my 3.4.

I can't speak to Mobil 1 in my rig. I have some friends in aviation who lived through the whole sludging thing that Mobil put them through and I have had a distrust of Mobil ever since. Too many lies back then and the tiger doesn's change it's stripes.

I will see if I can get some of my analysis sheets together and add my thoughts and see what I come up with.

 

I ran Mobile 1 syn 10w30 in my '93 turbo Eclipse for 8 years changing it at every 3500 miles and no sludge build up at all when we dropped the pan and remover the head after 100k.
I changed the oil at 3500 (twice a year) due to the rigors of drag racing over a season which was about 18-20 trips over 5 months.