Bought when new a 04 explorer with the 4.0 engine. I usually use Costco or Kwik Trip gas. Every 3 to 4 years after filling the gas tank, the gauge will not go to the full mark. You have to drive for 20 to 30 minutes before it reaches the full mark. With trial and error I have found by using the recommended amount of MMO in the gas it will take about 2 tank full's to go back to registering the correct amount after the fill. I'm not a mechanic but a better DIY after owning a Ford product.