OK...mind you I have never been a soft right pedal kinda guy since I love to blast through twisties and also drag race. But, when driving the huge "loafa' bread" I try not to "cruise" above 65-68 mph. I just feel like it's a more comfortable cruising speed that keeps my wife less tense and maybe, MAYBE, saves a tiny thimble of fuel.
BTW, does anyone use a
https://www.scangauge.com/ . I bought it for our old MH because it didn't have a tachometer. Now, I use to monitor a bunch of other functions, but also mph. It shows a speed roughly 3-4 mph slower than the speedometer. So, I bump my speed up to the speed I really want using the scangauge.