I noticed mine doesn't go all the way to the top digital bar ... even when I do fill it up to the gas cap. It goes up to the 2nd from the top though. It seems like the gauge goes down pretty reasonable, and it doesn't fluctuate as much as I had expected. I thought it would go from 3 bars to 0 bars up to 4 bars, etc., but it's pretty consistent from what I've seen. I think I had 3 bars left when I put in 7.3 gallons on my last fill up. We're scheduled to go up north again next Thursday, so I hope to get some ideas on how much gas in the tank relates to the digital display.