My 2023 Dodge Rebel HEMI 4X has about 2,000 miles on it, and if it's like my 2021 Dodge Sport HEMI 4X, the mileage will improve slightly when the odometer is closer to 5,000 miles. According to my window sticker, combined city and highway driving should be about 19 miles per gallon, and now I get about 16-17 miles per gallon.
One thing that helps me improve my gas mileage is having the fuel economy gauge on my tile screen. I've learned from experience that driving a 400-horsepower truck like you drive a 400-horsepower sports car will ruin your truck's fuel economy. If you watch your fuel economy gauge, you can see how quickly a sudden acceleration or stop-and-go driving reduces your gas mileage. To improve your fuel economy, accelerate when necessary, but drive at a smooth and constant speed whenever possible.