Mobil 1 in W123 -- Update

[Jeremy5848]

My 1985 300D Turbo (CA version w/trap cat, EGR and ARV disabled) has had Mobil 1 oil in its engine, transmission, and differential now for awhile so I wanted to report to the group. There are all sorts of posts here about the good and bad things that happen with Mobil 1. Here's what I've seen so far.

Engine [Delvac 1, 5W-40] 2300 miles (mostly highway). No measurable increase in fuel economy (24-25 MPG highway, 21 MPG city). No leaks. No oil usage (or at least, none that I can measure). I plan to change oil at 5000 mile intervals now instead of the 3000 mile intervals I used for dino oil. Easy start after sitting outside all night in 17F (-8C) weather after one 30 second glow cycle, no engine heater or battery charger was used. Wish it had been colder for a better test, oh well.

Transmission [Mobil 1 ATF] 1300 miles (all highway). No leaks. No change in the 'firm' 1-2 shift (some have reported smoother shifts).

Differential [Mobil 1 75W-90] No leaks. No howling or other noise, before or after the change. (Squirt bottle form factor made adding the new oil easy, a plus.) Old oil was clean since it was new when I did the axle job about 7000 miles ago.

So I'm satisfied, except that the stuff is so bloody expensive. What have been your results and observations?

Jeremy