Why all the false info? GM recommends the 6.2 only run Premium fuel, which where I am is $0.20-0.30 per gallon more than diesel. Yes, the 6.2 can run on 87 octane fuel but you will give up some of the HP/TQ specs that the 6.2 has. To get peak HP/TQ, you have to run 92/93 octane fuel.
Now, lets do some math based on 87 octane vs diesel fuel with some costs based on fuel prices from southern Indiana. These prices will be based on Walmart Fuel Center who does have the cheapest prices per GasBuddy.com in my town.
87 Octane - $2.69 per gallon
89 Octane - $2.99 per gallon (same as diesel)
93 Octane - $3.29 per gallon (10% more than diesel)
Diesel - $2.99 per gallon (11% more than 87)
Now, in my '20 3.0 4wd it has a lifetime average of 26.693 mpg over the 18,135 miles on the truck. Are you getting even close to that with the 6.2? I have a couple '17 5.3 2wd trucks in my fleet and they are only getting an average of 17-18 mpg. My 3.0 is getting roughly 45% better mileage than the 5.3's. I'd say that it is worth the extra cost of the diesel fuel.
The maintenance cost are not that much more. I came from a '16 Colorado 3.6. The dealership charged me $64 to change the oil and rotate the tires in the Colorado. They charge me $79 to change the oil and rotate the tires in the 3.0. GM recommended the 3.6 get oil changes at 5,000 mile intervals. The 3.0 is recommended to change the oil at 7,500 miles.
The attached image is from the EPA's website with the above fuel prices put in for customization.
I'm not saying stay away from the 6.2 as if I couldn't have gotten the 3.0 I'd have the 6.2. I would not ever get the 2.7, 4.3, or 5.3.