Unplug the wire to the sender, needle at the guage should go all the way up, short the wire to ground, needle should go all the way down. If this works, it´s probably your sender (by the oil filter). Wire/connector to the sender has been known to get messed up, when changing a stubborn filter.
The connector at the gauge cluster has been know to mess up. There is fuse for most of the guages. Normally wouldn´t cause just one gauge to mess up though.