Just wanted to add some information as well here. This is from Justin, the tuner here at BBP. This is regarding a 17 Yukon 6.2
"the 6.2L L86 engine requires 91+ octane at all times for any sort of efficient operation. Lower octane will result in up to a 50hp loss from potential as well as 2-3mpg reduction (even more with AFM disabled) and unpredictable throttle application. This is due to the 12:1 compression ratio, the use of 87 octane results in constant pinging."
"We are not able to provide an 87 tune on a 6.2L engine. We can only provide a 91+ tune. You can run 87 on that tune if you would like, but we can only provide a 91+ tune. The factory programming is already set up for a minimum of 91 octane, as outlined in the owner's manual. It can run on lower octane by pinging and compensating for that pinging, but it cannot be "tuned" as such."
"the 6.2L L86 engine requires 91+ octane at all times for any sort of efficient operation. Lower octane will result in up to a 50hp loss from potential as well as 2-3mpg reduction (even more with AFM disabled) and unpredictable throttle application. This is due to the 12:1 compression ratio, the use of 87 octane results in constant pinging."
"We are not able to provide an 87 tune on a 6.2L engine. We can only provide a 91+ tune. You can run 87 on that tune if you would like, but we can only provide a 91+ tune. The factory programming is already set up for a minimum of 91 octane, as outlined in the owner's manual. It can run on lower octane by pinging and compensating for that pinging, but it cannot be "tuned" as such."