I have a 2020 2500 standard output. After I idle somewhere for a little while maybe 15 minutes plus I notice when I start back driving the mpg when driving is way lower than normal. Can hardly get it to stay over 10mpg even when cruising at 45. If I park the truck and turn off then next time I drive it it’s back to normal. Truck has 1500 miles on it. Anybody else have this issue?