Oil viscosty and engine temperature

[Rick68]

Will running a thicker viscosity oil increase engine temperatures?

[X33RS]

Nope, not that I've ever seen or read reports of.  I've run Amsoil products for years, in particular their 20w-50 high zinc line.   Their cold pour temp in the 20W is actually better than alot of your 5W's and most of your 10W's thanks to the superior additive package they have.

Here's a chart to compare, just scroll down.  The Amsoil 20W-50 has a pour temp down to -47 degrees.  Compare that to others and make your choice.  Some of the 5W's and 10W's don't really fare that well and won't even come close to the flow abilities of the Amsoil 20W..

It's all about which brand you want to run and the additive package they use.

http://www.bestsyntheticoil.com/amsoil/printable/chart.html 

[X33RS]

If it makes you feel any better, I drive mine in the 110+ AZ heat and they run just fine with no heat issues, and run just as well up here at 5,000 feet where winter time temps can dip to freezing for a couple months.  So I see alot of adversity in ambient temps.

[Rick68]

I am running Brad Penn 20W-50.I was originally running Castrol Syntec 5W-50.My engine is a 396/375hp.The engine is done all stock including exhaust manifolds.It is just running a lumpier camshaft.