02zx9r,
Not looking to pick a fight or split hairs, but the Rotella 5W-40 doesn't strike me as on the thin side. At 100 deg C the kinetic viscosity is 15 cSt. This compares favorably with HDEO 15w40s such as Delo (15.7), Rotella (15.5), Castrol Tection (14.9), and Mobil 1 TDT (14.9). Then there are the PCMO 5W-40s, all of which are lower; e.g., Valvoline Synpower (14.5), QS Q HP (13.1) and Pz Plat (14.5).
I certainly agree with you about not worrying about using it in just about anything--it's almost a universal motor oil. And the price is right.