I haven't been on here in awhile, but wanted to share this with you stock guys. I started using Lucas Oil Upper Cylinder Lubricant about 3 years ago, I add like 4-6 ounces in my fuel every time I fill the tank, and I have to say that this stuff works. After using it for like 6 weeks I started noticing that my Ex was running a little better and a little smoother. Lucas oil products are always a good choice. I regularly try to use at least the mid-range gas, and I know that helps a bit as well. I also changed my fuel pressure regulator, after 140k its a great idea to do this, as well as remembering to change you fuel filter. I clean my engine with Bg 44k fuel system cleaner once a year as well, it is great stuff, cleaning deposits off from bad gas. I run NGK Iridium spark plugs and wires, added on a cold air intake, and clean my MAF sensor once a year. I also upgraded my 02 sensors to the NGK brand. I have done a ton of maintenance on this Ex over the years, upgraded exhaust, I threw on a Magnaflow Muffler and Flowmaster Cat. I threw some slotted rotors on the front, had my driveshaft balanced, swapped out the U-Joints to the Spicer brand, and added converted my auto hubs to Superwinch manual hubs, which are very durable, there is a set that fit 1st gen explorers that may not be easily found online. As far as oil changes, I use K&N oil filters, they are super nice because they have a nut welded onto the bottom so changing your oil just became easier. One thing that is up in the air is changing tranny fluid, but I did it and it did help ease the shifting after. Maintaining a healthy Ex is not that hard, and in the long run, it will save you money, especially if you put a lot of miles on. I have almost 300k on my Ex right now, and I would like to think it has a lot to do with the things I detailed above. Feel free to share things that have helped you out in the fuel economy and performance department. I will update this thread if I can think of other things that have helped.