Tow haul usage

[PBANDJ]

New to forum.

Purchased a new Silverado 1500, will use to pull my travel trailer @ 7000 lbs. New truck has max tow package, 6.2, 10 speed transmission , 3.42 gearing. I have used tow haul before in a Dodge truck when pulling a grade and going downhill grades in the Sierra Nevada mountains. When on the flat roads and interstates I use to just leave transmission in drive with no issues. The former Dodge had the 5.9 Cummins with auto transmission.

I do understand what the tow haul does with the current new truck but would like to know if leaving it in Drive will work in the flat land towing. Of course I ask this because I used to do it with the old Dodge and had no problems as it gave me better mileage on a long trip. Does anyone have experience with the 6.2, 10 speed transmission and 3.42 rear gear and pulling as stated above with a comparable  7000# Travel Trailer in flat land without tow haul engaged, if so what is your experience or opinion. Thanks for your reply’s in advance.