I use Chevron Delo 400 15W40 in everything including the lawn mower, except my new car which gets Mobil One 10W30.
I agree with your list of agreement except the last one. In an obscure thread months and months ago, there was some reference about mixing synthetic and dino. There was someone responding who was in the oil industry and sounded very knowledgable. He said that part of oil specificaiton is mixability, and that there was nothing wrong with this mix, and actually some to ge gained.
This mixability also applied to any SAE spec oil mixed with any other. This was a shock to me, but I have no reason to doubt him.
You are in the same situation as myself. It is extremely rare that my cars don't go at least 20 miles every time they're started. This does allow extended oil changes. To help it along, a hot thorough drain is good measure. I am a fanatic oii changer because I have had such good luck with it in the past. When it does come time to open up one of my engines they are always as clean as can be and you never find any crud even packed in the ring grooves.
I wish I could help with the unpredictable drivers, I guess frequent oil changes can't do much good for that.
Thanks everyone for your comments,
[Edited by LarryBible on 01-04-2001 at 07:50 PM]