I have noticed my gas gauge seems to fluctuate a lot. Often times I will be driving a short drive and it will go down an 1/8 of a tank and then the next time i get in it is back were it was before. Other times it appears to be moving around more than it should while driving. I had a tiburon with approximately the same size gas tank and after 8.5 years my gauge was extremely accurate and never fluctuated. I have been parking on flat surfaces, hilly terrain is not the issue. After a few fill ups it appears to fill according to what is left in the tank, but the gauge just seems to move around a lot more than I am used too when driving.