Nearly everything on my '91 Saturn is inoperable, including the odometer. The gas gauge is also partially inoperable. When the level gets below 1/2, the needle will swing between 1/2 and empty, then as it gets close to 1/4 tank, it swings between 1/4 and empty.
I'm not about to put a new gauge in that old beater, so I just put gas in every so often, and remember when. If I'm driving further than a few blocks away, I'll put gas in just to be safe. I usually only need to put about $15 a month in it.