My 89, the gas gauge drops with ignition off.
If you disconnect the battery completely, does the gauge fall?
Oil pressure reads low, and is inaccurate, and readings are delayed about 45 seconds as to correlating to actual oil pressure. I T'd the line and installed a mechanical OP gauge 14 years ago as the stock gauge was alarming me. I've got plenty of oil pressure though.
The temp and gas gauge are expecting 5 volts from a regulator that converts it from 12.x+ volts DC. This ancient regulator design goes back to the 1930's. It is adjustable, but one would need an analog voltmeter with a needle, not a digital one.
Mine started acting haywire and temp and fuel gauges would read high and low swinging together.
I replaced it with a DC to DC converter as it was 8$ opposed to the 40$ for 1930's era tech.
I am not sure how different a 92 is from an 89, but the gauge cluster is pretty simple. There is one indexed round connector and corresponding pins on the backside of the cluster. One of these pins is for ground.
I resoldered all the pins, and made sure the ground pin was actually well grounded, I think it grounds at the base of the headlamps switch but cannot remember for sure
Your Gauge cluster might be screwed, but I'd check to see if the ground is good and all the connections back there are sound.
Get some Caig DeoXit D5. Use it on every electrical connector you open before reseating.
No other electrical contact cleaner comes even remotely close, but they are good for flushing out old crusty dielectric grease, as the Caig is too $$$ for that task.
I tried to look up the gauge voltage regulator on Rockauto, couldn't find it for your year or mine, though it was there in the past.
It is metal housing, about 1.5 inches long 1/2 inch wide with 3 legs which plugs into the back of the cluster.
Back when I had a flip phone and was on the limits of 2g coverage, it, seeking a tower could make my temp and fuel gauges rise and fall 20% rapidly, and would freak me out.
This is the dash regulator I have been employing for many years. I can access the adjustment screw. 5.5 volts will raise the fuel and temp gauges almost a full hatch mark over 5.0 volts.https://www.amazon.com/Converter-DR...regulator&qid=1617126279&sr=8-27
Once in the many years since I installed it did I have to readjust it, as it had drifted up to 5.3v and my temp gauge started reading high. I installed a 3 decimal voltmeter temporarily so I could watch it. If my temp gauge ever starts reading higher than expected this is my first suspect.
Shine a light inside the connector on your one wire temp gauge connector. Mine recently was found to be growing a lot of pretty blue green corrosion.