Date registered: May 2011
Vehicle: 2005 S600
Location: Virginia Beach
Mentioned: 13 Post(s)
Quoted: 53 Post(s)
It should hold its height for several days. Beyond that period of time, some sag is considered normal.
Generally, it's internal valve block leakage. A rodeo and fluid flush, with new ABC filters, would be the first thing to try. Next is a removal of the valve blocks, disassembly, cleaning, and o-ring replacement. The latter fixed the sag in my ABC car.
2016 Tundra 1794
2005 MB S600 (100K, Michelin AS3+, M1 0W40)
2002 V70-XC (228K Castrol 0W40)
2002 V70-T5 (198K, Mobil 1 0W40)
1932 Packard Sedan (straight 8, dual sidemount spares, original paint and interior, Shell Rotella 15W40)