Someone is putting it there. There is no way for oil to get from the engine to your fuel tank by natural means. Literally, if you have oil in your fuel tank, someone is sabotaging your vehicle by putting the oil there.
Getting rid of an old oil tank is a difficult task. The oil will have to removed first. You may be able to donate the oil. The tank must them be cut in half in order to get it out of the house. Call your local trash collection company to find out where you can take the tank for disposal.
Some truckers use the oil from an oil change as added fuel in the tank. In this case it will Not ruin your tank
The question is how did oil get in the fuel tank? If there was very little oil put in the tank as in less than a couple of quarts then just fill the tank full and drive the car. The oil will be burned with the fuel and will do no harm. If there was more than a couple of quarts, you can siphon it out with a hand pump. You can get enough out to then fill the tank and drive the rest out.
Here is a tank chart that should help. Generally, the oil tank has a bit of "headroom" at the top, so, for example, a 275 gallon tank only holds about 256 gallons of useable fuel. Check with your local fuel company to determine the useable fuel volume your tank contains. http://www.sippin.com/oil%20tank%20measure%20chart.htm
The fuel tank is either out of gas or the fuel line is clogged.
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You may have a bad fuel pump, no fuel in the tank or a blocked fuel line.
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No it will clog up the fuel filter unless the fuel tank is heated.
open the fuel tank filler cap and dump the fuel/oil mixture out.
The fuel gauge could be getting improper signals from the fuel sensor. The sensor is located inside of the fuel tank.
16.0 gal. fuel tank 5.8 Quarts or 5.5Litres with the filter by my manual on a V6 .HHH Tracker has a11.1 gal. fuel tank. Your oil is most likely wrong too.