Interesting article concerning viscosity and the Coyote engine.
They specifically recommend 5w20. Below are several quotes from the article.

"The higher viscosity, the hotter the engine will run. Think of an engine like a giant mixer. The thicker the material in the mixer, the hotter the motor will get, it’s the same thing with engine oil.” Those higher temperatures lead to a faster loss of oil viscosity, and also higher engine operating temperatures which can contribute to wear or even parts failure."

And this.

“Unless you’re changing bearing clearances or the oiling system, you should stick with the factory recommended viscosity,” says Speed. So in modified Coyote and modular engines, Driven’s FR20 engine oil offers the benefits of OE recommended viscosity, with better volatility and VI than an off the shelf product.
While some enthusiasts balk at the idea of running lightweight viscosity oils like 5w20 in their engines, the truth is that overhead cam engines rely on those lightweight oils. Unlike a a cam-in-block engine, the camshafts are all the way at the top of the cylinder head, the last place to get oil. This means that when the engine is cold, it’s critical for oil to reach those camshafts as quickly as possible creating the need for a lower viscosity oil.
Changing to a higher viscosity oil can potentially slow down the progress of oil reaching the cams in a timely manner. When you throw in the pressures needed to operate variable valve timing system like on Coyote powered Mustangs, having the proper viscosity is even more critical, since the engine relies on hydraulic pressure from the engine oil to operate."

Full article here.
http://tinyurl.com/lazaoeb

 

And here we go again.

 

I run straight 90 weight gear oil in my coyote because I like the way it sounds.

 

Track Pack cars spec 5w-50 and non track pack cars call for 5w-20. Same exact engine. So that alone contradicts their statement.

 

Excellent point.

 

Thus the "5" part of 5Wx. Jeez.

 

Oil on this forum seems like religion, everyone thinks theirs is better, interesting stuff none the less.

 

5w-50 Motorcraft isn't the same as a 5w-50 of a different brand.

The Track Pack cars are apparently expected to be tracked. The 50wt holds up longer to the same amount of heat as the 20wt.

That's it.

Street car = 5w-20

On track = 5w-50

 

Correct. In fact the Motorcraft 5w-50 is some of the worst oil at there as it shears quite quickly.

 

50w50isnt same as 5 w 50?

 

I use 5 30 Mobil one xtended use in my stock 12 5.0!!I doubt if i,m putting the wrong stuff in even though it calls for 5 20 ,what would be the harm?

 

Nope, I'm using Amsoil 10w-30.

 

And the Track Pack cars have a larger Radiator and an Oil Cooler, both from the Boss. So heat dissipation with the thicker oil is not a problem. I stick to the 5W-50 recommendation on my oil cap.