I'm probably within 2 to 3 weeks of making a decision on which way to go., The only article that I could find said GM tested the C8 in a area where the average summer high was 105F with the Z51 package (3 radiators).
I really wanted to hold off on the Z51 package but that brings me down to the 2 standard radiators. We live in the desert southwest where temps can reach 117F/120F at times. Common sense tells me 3 radiators are
better than 2 but not wanting the Z51 pkg I thought I would reach out and see if the forum had any addtnl info that might make my decision easier. TIA.

 

Are you going to be on the racetrack at 120°. Normal street driving in Phoenix, or Death Valley for that matter, without the Z51 package will be just fine. I lived in Phoenix, I never had any cooling issues with any car, ever. The extra cooling on the Z51 is to handle the high heat generated from max performing the car on the track, not needed if not tracking the car so it’s not included on the non Z51 model. I live in Texas, it gets hot here too, I’m not ordering Z51.

 

I agree you. I live in the Phoenix area and haven't ever had cooling issues with any car I own.

 

I'm getting a Z51 but not for the extra cooling (I don't plan on tracking my car), but it doesn't hurt.
I wouldn't be concerned about the cooling, even in the hottest street conditions, if you're not planning on tracking your car.

 

Also getting Z51 with Mag Ride. I like the added cooling although it’s not necessarily needed at our Summer place in WA. It can get toasty at our Winter place in AZ in late May into June. I’m getting it because I had it on my C7 and loved the handling it offered. The 8 speed got pretty toasty the one time I took it on a road course but with the DCT I don’t expect the same issue.

 

That 3rd radiator provides what Tadge called "supercooling." Technically don't like the term used for reducing the water temp coming from the front rads BUT he said it adds cooling NOT to just the engine BUT also the DCT. That is critical to it's performance. There is a large Liquid/Liquid heat exchanger that sits on top of the DCT. DCT fluid temp is very important to the performance of the two wet clutches.

Heck if you're going to get NPP it's included with the Z51 so deduct that extra cost. You get better larger brakes and higher performance tires. IMO also a big advantage is eLSD versus 1960's Positraction technology! Also get a 5.17:1 dif ratio for quicker 0 to 60 times. Oh yea a 3rd radiator!

 

But It's a Dry Heat!

 

I live in NV. I have/had (sold it) a 2020 non-Z51. No issues with heat.
I have a 2021 on order, same exact spec, 1LT, non-Z51, black 5 spoke wheels, edge red calipers, NPP exhaust.
Why non-z51:
I will not be tracking the C8. (I did take the Ron Fellows class).
I wanted all season tires.
The summer only tires crack in cold weather (see below).
I was in Denver on July 4, 19xx and woke up to 12 inches of snow!
I did not want the brake dust.
Yes, I would like to have the extra radiator (not needed).
Yes, I would like the larger brakes (not needed).
Don't like a wing on the back.
I added the front splitter.
Page 249 in the owners manual:
High performance summer tires have rubber compounds that lose flexibility and may develop surface cracks in the tread area at temperatures below −7 ° (20 °F) or less, let them warm up in a heated space to at least 5 °C (40 °F) for 24 hours or more before being installed or driving a vehicle on which they are installed.
Tire Rack:
Note: Tires exposed to temperatures of 20 degrees F (-7 degrees C) or lower must be permitted to gradually return to temperatures of at least 40 degrees F (5 degrees C) for at least 24 hours before they are flexed in any manner, such as by adjusting inflation pressures, mounting them on wheels, or using them to support, roll or drive a vehicle. Flexing of the specialized rubber compounds used in Max Performance Summer tires during cold-weather use can result in irreversible compound cracking. While compound cracking is not a warrantable condition because it occurs as the result of improper use or storage, tires exhibiting compound cracking must be replaced.