I've been running Schaeffer's in the family fleet for several years. Everything looks clean except the the usual brown staining in the pores of the aluminum castings. No sludge, varnish, or crud of any kind when looking at the camshafts and area visible down the oil filler.
Here's a representative analysis of the syn blend 5W-30 after 10,018 miles:
Iron--16 ppm
Aluminum--1
Viscosity--10.5
Oxidation--.04 (Staveley's scale)
TBN--6.0
"No corrective action required."
I continue to use Schaeffer lubes in everything...cars & pickup, mowers, generator, snow blower, motorcycle. I'm now using the 5W-40 full syn in the turbo Volvo* and the air cooled summer equipment, 5W-30 full syn in the other car & pickup plus the air cooled winter equipment, 20W-50 syn blend in the motorcycle and one mower that runs really hot (will switch to 5W-50 full syn when the 20W-50 is gone). One subjective note--when switching to Schaeffer's 20W-50 syn blend in a used motorcycle, after a few miles, the engine just feels and sounds like it is running more freely. I've had this happen twice; one cycle had 10W-30, the other 10W-40.
*Latest analysis of the 1996 Volvo 850 turbo with 165,000 miles on it showed the 5W-40 at 9000 miles to be in excellent condition, "retest at 11,000 miles." I changed it at 10k just to keep the intervals even.