GM-GMC: temp and gas gauge on 1999 van, gmc savana van, gmc savana

Question
I own a 1999 full size gmc savana van. The gas gauge and oil gauge flucuates continually. The temp. gauge and amp gauge seem to be okay.

Answer
There are two possible causes for you concern.  The first being a faulty Instrument panel cluster.  In order to know for sure you would need a scanner to display the inputs to the cluster and compare them to the outputs or what the gauges actually say, if it isn't displaying what it should, replace the cluster.  The second this that could be the problem is more for the fuel gauge than the oil gauge.  The fuel level sensors are prone to malfunctioning.  There are small tabs that ride up and down on a resistor insided the tank depending on the amount of fuel in the tank.  The small tabs break off or bend out of position rendering the sensor useless or inaccurate.  Both are equally likely.  I would explore the cluster issue before pulling the fuel tank out.
hope this helps