I agree that you should not use Mobil 1 on an older engine but not for the reasons stated.
A few years back, my daughter had a '93 FFFF Probe (sorry about the four letter word) with 230,000 miles. Actually, it's a mazda with a blue oval on the hood. Ran well and used no oil between 3,000 mile oil changes. The hyd lifters were on the noisy side. With Mobil 1 that thing was so quiet, you would never suspect it then wanted a quart every 600 miles. Going back to regular oil did not quench its thurst. Valvoline Max Life reduced the consumption to 800-1000 miles but the damage was done. There seems to be, no going back. I wouldn't know about smaller molecules. I think it simply cleans the sludge and varnish from around the seals.
