You got me beat.
I ran a UOA, which, due to top-off, wound up being:
4 qts Supertech 5W30 Conventional
1 qt Rislone
1 qt GC
Supertech and Rislone mixed isn't too weird. Adding GC probably made the little Teutonic Elves cuss so bad they had to go to confession right afterwards.
My dumbest combination was filling my '78 Mercedes 240D with Shell Rotella T 15W40 (good choice). But when it used (leaked, mostly) 3 qts per 1000 miles, I ran out of Rotella T and started topping off with the closest I could find at the conveniece store. It was frequently Castrol GTX 10W40, which I don't even recall being diesel-rated (bad choice). I'd be afraid to try that today due to shearing and additive concerns.
I suppose with my drain rate, I was effectively running 2000 mile OCIs, which should have let me run *ANY* oil as long as I changed that freaking half-gallon-sized Mann filter.