Gentlemen: What motor oil do you use?

I run 10w 40 year round in everything I have, from the slant in my 85 D150 to 318 in 78 fury, 318 in 96 Dakota, 3.9 In a 99 Dakota, and a 360 in a 01 durango. There's a place nearby that sometimes runs a he11uva sale on mobil 15w40 diesel oil, when I catch the sale I'll stock up on some and run that in the hot weather months.
(Talking hot by Chicago standards) otherwise it's dino 10w40 year round. In everything but the mowers, and then they get 10w40 when I'm out of straight 30