Back in 2005, I converted my "low pro" 24.5" standard duals to Michelin super singles (tire pros call them wide based singles). I weighed the truck before and after, and lost 440 lbs.
It may seem insignificant to lose 440 lbs when talking about an 80k lb truck, but it was a huge help to me. I was able to run with more fuel on board, rather than skimping along to maintain a legal weight. Another big benefit was improved ride; half as many side walls flexing certainly saved fuel but also created a softer ride. Very nice handling was a bonus. The "supers" are so easy to chain up, too. I could cut my time chaining drastically and that was a big deal when on tight schedules.
I ran super singles for about ten years and nearly 1.5 million miles. I lost two of them in that time. One popped in a truck stop parking lot, the other went kaboom on the high plains of eastern Colorado. I now have a very light weight truck with the good ol' traditional duals, but if needed, I could shave off another 400 lbs by converting.