Here is what Royal Purple had to say;

" What is really of concern is the oil temperature you run and the oil pressures you run at those typical oil temperatures. If this vehicle is used only as a street and occasional drag strip car, there is likely little benefit to going heavier because the oil isn’t being heated much more than before. In a street vehicle, just because an engine can make a lot of power doesn’t mean that it usually does. It doesn’t take much power to move a typical vehicle in typical street use.

On the other hand, if the vehicle is used for road track and/or endurance events where the engine will be used to its full potential for extended periods, oil temperatures will typically be much higher. This would be a good scenario to consider a higher viscosity engine oil. Going with a 10W-40 will cause no harm, but likely not provide any benefit either. Royal Purple’s Synerlec additive technology is providing extra protection independent of viscosity. If you want to do it, it will be fine. I, personally, would run the HPS 5W-30."

Needles to say I am still sticking with 0w40 and we will see what the results show.

 

Running a thicker weight oil in high stress / high heat conditions will help maintain appropriate viscosity under those conditions. In built engines with greater clearances it may also help maintain oil pressure and minimize oil consumption. The downside is that the engine will experience greater cold start engine wear.

In cold weather, you will not want to run a 20/50 oil. In Texas it may be fine. I think a 0W-40 is a great oil for cold regions. Many use Rotella T6 5W-40 (this is what I use in NC) or Mobil 1 TDT 5W-40. I would have no problem running a 15W-40 or even 20W-50 oil in the summer, but I wouldn't do it during the winter here (temps sometimes drop to freezing).

 

Appreciate the reply. I figured as much as far as temp+viscosity and oil press. I'm currently running Mobil 1, 0w40 for winter and have Rotella t6 5w40 waiting for the spring/summer. Heard good things about Shell.