My '99 Expedition that has been exhibiting the piston slap at cold start-up that's been discussed of late. Ford's technical buletin recommends using Mobile 1 synthetic oil to hide, but not fix, the problem. According to Ford, the slap won't damage anything long term, but just sounds bad.
I changed the oil this weekend using Valvoline synthetic and so far so good! Slap is gone to the ear and idle is much smoother.
Also, my dealer found the undercarriage "thumping" that no-one has been able to diagnose (threads from a few months ago about noises from under the back seat): a top shock-nut was loose in rear. This was hard to find because when up on the rack, the weight of the rear end was hanging on the shock nut so that one couldn't find the rattle by shaking everything by hand.

On to more enjoyable weekend endeavours.