Originally Posted by finrisk
Does the new Hemi engine really has variable valve timing and if so, can somebody please explain in simple terms how it works on this engine, e.g. is it hydraulicly or electrically activated and how does it get activated?
Is it still necessary to use 5w-20 oil in this motor? What will happen if one uses a thicker viscosity oil, such as 10w-40 in hot areas, such as South Africa? Will it interfere with the MDS and if so in what way?
Thanking you in anticipation.
The VVT is really more of a VCT (Variable Cam Timing) and like the MDS, it uses the engine oil as the hydraulic medium controlled by electronically controlled valves or phasors. Everything is timed based on the fluid dynamics of a 20W oil so no, you cannot run thicker oil in hotter climates. BUT, there's nothing in S. Africa you'll encounter that's hotter than the SW US where this engine has been extensively tested.
With modern oils and computer controlled cooling systems the idea that thicker oil protects better in hot climates is becoming more urban legend than fact. A modern 20W synthetic is more sheer and viscosity stable than the best 40W oil of a decade ago.