My 2005 Yukon Denali XL AWD 6.0l with 275,000 miles will get about 14-15 on the highway, but I am not very nice to it, usually 65-75 MPH. Over 65 the MPG starts to crater.
If I slow down and drive 55-60 MPH it may get high 15 MPG or close to 16 MPG but that's tops.
If I hang an enclosed trailer on the back, mileage drops to close to 10 MPG regardless of speed!
My 2024 has been able to get close to 25 MPG on red roads, fairly flat 45-55 MPH without stops or traffic. But hitting the highway hard dealing with and working my way around traffic about 18-19 MPG, sometimes a bit higher depending on traffic. The right foot really hurts the economy, but I can sure get around traffic!