Where does the manual call for it?
In the 2021 manual the following are the only sections I could find referring to additives. Which say, use a specific quality of fuel; if you don't have that use the GM additive. Which is different then use additives.
From the manual:
https://my.gm.ca/gmc/en/content/dam...gmc-yukon-xl-denali-owners-manual-english.pdf
Fuel Additives
TOP TIER Detergent Diesel is highly recommended for use with your vehicle. If your area does not have TOP TIER Detergent Diesel, GM recommends the use of ACDelco Diesel Fuel Conditioner. This will help maintain optimal engine performance. GM does not recommend other aftermarket diesel additives. If low-quality diesel is used for refueling, GM recommends adding ACDelco Fuel System Treatment Plus-Diesel to help clean engine deposits. This is available at your GM dealer
Use of fuel that does not comply with the required technical standards can lead to engine power loss, increased wear, or engine damage and may void your warranty. Some improper fuels are:
. Diesel fuel with the addition of gasoline.
. Diesel fuel mixed with engine oil or automatic transmission fluid.
. Triglyceride fuels, such as raw vegetable oil or animal fat, in any form, including with blends of diesel or biodiesel.
. Marine diesel fuel and fuel oils.
. Diesel-water emulsions, such as Aquazole.
. Aftermarket diesel fuel additives, which contain alcohols, organo-m