I have a '98 XLT with the 4.0L SOHC. I get a pretty steady 14-17 mpg combined city/highway depending on the season. Anything I can do to improve my mileage significantly? I mean beyond keeping the engine tuned up and air cleaner element clean. Before I bought my truck everyone told me I could expect around 20 mpg but I have never gotten close to that.
I've heard about a product that you install after the air cleaner and its supposed to impart a swirl or vortex to the air being fed to the cylinders and result in more complete combustion and better mileage, but it sounds like a marketing gimmick to me.