Simviation Forums

Has anyone had their fuel fluctuate while flying?  I was flying a Mooney Bravo the other day and drained the left fuel tank to empty.  I checked under change fuel and it was at 0.  After a few minutes of flying on the right tank which was down to about 1/4.  Both guages began to rise.  I ended with 1/4 tank on left and 1/2 on right.  Any idea why this happened?  This is not the first time either.