94 gauges question

I have a 94 25th and the gauges seem to "float" all over. I drove 242 miles today, the gas tank was full when I left, it was at 1/2 tank when I returned, it took 11.7 gallons to re-fill. Manual says its a 15.5 gallon tank. Oil gauge only shows 30psi when cruising at 70 miles an hour sometimes, other times shows 20psi, shows 40psi when cold. Amp gauge reads anywhere from 13.5-15.0. Seems like every time I start the car the gauges jump to a different point, whats up?

Fuel gauge is inaccurate due to the shape of the gas tank. We all had/have that problem.
As far as the oil pressure gauge, oil pressure depends on engine speed, not car speed. So your RPM's dictate how hard the oil pump is working. If I remember correctly, you'll see high oil pressure from 2K on up. High pressure on a cold engine is normal, cause the oil needs to warm up. You only need to worry when you lose all oil pressure when driving...bad news.

This is pretty common in my 94 also. I replace the oil pressure sending unit. It’s easy to fix. You just unscrew the old one and put the new one in and hook up the wire. Mine read 20 psi and was leaking oil. It now reads about 80 when cold and 40+ most of the time. The sensor is a pressure diaphragm, so the more pressure the higher the reading. My gas gage is just like yours. At 1/2 a tank I have about 5-6 gallons left. When it says empty you better be getting gas, it’s not lying.