Magnatec replacement...GTX FS or Edge?

Got 2 oil changes worth of the QSFS....It'll go in within the next 6 weeks probably. I always use the towing yet, just back and forth to the work dungeon.
Did that for 35 years. Half of those years surrounded daily 100-mile commutes! Nowadays at 56 years old, I'm only entertaining home-office jobs surrounding telecom engineering and project management.

This reminds me... I need to accomplish one more round of fluid change-outs in my old Silverado, while I can outside. It needs engine oil and transfer case fluid changes before the snow sticks here (it snowed today but didn't stick). Soon!

Come to think of it... my AWD/4WD transfer case is all original, with approximately 205,000 miles on it! I figure that's a miracle given its constant use -- half the year -- in the AWD or 4WD positions. I hope its because I am somewhat religious about Auto-Trak II fluid change-outs.

I can tell you the auto-locking rear diff is NOT original (not as religious with that one). Oops.
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EDGE if the price is good - even then , why would you buy any Castrol oil over M1 , Pennzoil or Valvoline synthetic oils ? The Castrol add packs , base stocks , etc. in the synthetic oils shipped to the USA are on the "meh" side of performance / quality .
I think Edge EP would preform as well as Magnatec did.

Here's a response I received from Castrol back in February.

Thank you for contacting Castrol North America.
We apologize for the delay in our response.
Castrol GTX FULL SYNTHETIC is replacing Castrol GTX MAGNATEC to align with GM’s latest generation of GM-certified engine oil, GM dexos™1 Gen 3.
Castrol GTX FULL SYNTHETIC and Castrol GTX MAGNATEC are very similar formulations, with very similar properties and the GTX FULL SYNTHETIC product also contains the intelligent molecule like GTX MAGNATEC that protects the engine from start-up.
Castrol GTX FULL SYNTHETIC has been designed to meet the needs of today’s advanced engine technologies and to help extend engine life by fighting the impact of severe driving conditions. It provides the same outstanding wear protection of GTX MAGNATEC plus superior sludge protection that exceeds the industry standard.
Castrol GTX FULL SYNTHETIC is available in SAE 0W-20, 5W-20, and 5W-30 grades.
Castrol always recommends following the guidelines of the engine manufacturer for the recommended oil (i.e., SAE grade, API rating and manufacturer specifications) specific to your application. This information can always be found in the owner’s manual or by contacting the manufacturer directly. Before using any lubricant, ensure that the lubricant product specifications meet or exceed the lubricant specifications required by the Original Equipment Manufacturer (OEM) for that specific use.
Thank you again for contacting Castrol, we value your patronage!
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I have a feeling one could find almost the same text on Castrol's website. That's a canned response that was approved by their marketing and engineering groups for questions like yours.
Pretty much. And it took like a month to get that.
If you could choose Castrol GTX Full Synthetic or Kirkland FS (by Warren Highline) in 0w20 which would you use and why?