Be careful in your search. I recently made a switch from stock MTB tires to something smoother, I went with the Continental Contact Cruiser. I did notice an increase in speed (about .7 mph faster), but I had to work harder because the tires were heavier. The flats and downhills were nice but anything with an incline took a little extra compared to my stock tires. My stock tires weighed 640 grams each, and the new tires weighed 1025 grams each.
Dont know if it will help but here's a link to the thread I started regarding my tire change out ......
https://www.bikeforums.net/general-c...-smoother.html