That is the range mine was at too. When I switched to Royal purple, 5w20, idle went up to about 21-23, and I have seen 60 under acceleration.
2013 Charger R/T MAX -- Bright White
**Sold**-2006 Charger R/T -- Born 5/3/2006, Adopted 5/17/2006
Brilliant Black Crystal Pearl -- The fastest color.
R&T Pkg, Sound II, Elec Conv. Sun Roof
The Official "Black" Charger Thread