Gas Gauge Weirdness

[XterraVersa]

I know these are the most inaccurate thing but something weird has happened to mine.

For the 1st 18k+ miles I would get the following mileages on the trip meter:

F - 60 miles3/4 - 200 miles1/2 - 325 miles1/4 - 400 miles

Now for the past three tanks I am getting:

F - <10 miles3/4 - 100 miles1/2 - 200 miles1/4 - 400 miles

The mileage is still above 35 mpg but the 1st time it happened I thought a sensor may have gone bad or I had a bad tank of fuel.

[Ever Victorious]

My gas gauge has been doing that recently, but since the economy has not changed noticeably (except for the winter formulation switch), I've just ignored it.