Why does my oil pressure drop to zero when I pass another vehicle ?

Change the sensor. it appears to be a known issue.

https://www.autopartsrepairs.com/causes-low-drop-oil-pressure-dodge-ram-trucks/

Durango

https://dodgeforum.com/forum/1st-gen-durango/276936-oil-pressure-gauge-drops-and-rises.html

https://www.google.com/search?q=%2799+Dodge+Ram+1500+5.2L+Intermittent+sudden+drop+of+oil+pressure

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Another gauge needs to be connected to the car to check that oil pressure sensor or the gauge itself is not the problem.

If an independent gauge shows the same readings I would suspect a sticking oil pressure relief valve.

Hello, this problem is due to a failing stepper motor. The stepper motor is the motor behind the gauge that controls the
movement of the needle. When a stepper motor begins to go out it will cause the gauge needle to stick, skip around, stay
at zero or max out on the gauge. The only way to fix the problem is to replace the stepper motor with a new one. While
replacing one motor it is best to go ahead and replace them all as the others will go out in time as well. Youre cluster
will have one motor for each gauge. Here's a link to a page showing exactly how to replace a GM stepper motor and where
to get the correct parts to do the job!
DIY Finally How To Repair GM Instrument Cluster At Home Speedometer And...

the oil pressure gauge only gets a reading when the engine is runningas the oil is being curculated. when you shut the vehicle off it should go back to zero and be there until the vehicle cranks back up. i hope this helps

If your oil pressure is dropping to zero at an idle, then I would quit driving the vehicle. It is very possible that the engine is low on oil. Or that the oil pump is going bad. If you continue to drive the vehicle, you could ruin the engine. There is a oil pressure sending unit that could be bad. But if the oil pressure goes up when it is above an idle, then the sending unit is probably ok.

Thank you for being very clear, most of the people on this site write very little or very poorly.

On that note, on to options. It's either (in my expert opinion) an internal engine problem, or your computer/spark plugs needs to be replaced.

Step 1: Get a tune up, (100 bucks) if already done, than I'm proud of you.
Step 2: Go to a mechanic and shell out 50-80 bucks to get a specialized computer hooked up to your car to tell you any and all of the problems with your car.
Step 3: get overcharged by said mechanic to fix it, or do it yourself and grow some chest hair.

Hope it helps.

(excuse the sarcasm, I'm bored at work solving random car problems)

oil pressure relief valve is a possibility or the oil pump is worn ,either way its a sump off job

You probably need a oil pressure sending unit it is located at the back of the engine and is a high failure

Two things...when it reads zero, is there any engine noise (tapping or knocking)? After you rev the engine does the pressure read normal at idle and function normally, or does it go back down? Either way, you should not drive the vehicle 'till you have a mechanical gauge (yours is electro-mechanical) put on there and the actual pressure is tested. The condition may be a bad sending unit, a bad bearing or possible obstructed oil pump screen. The repair is obviously different for each one and the price is as well.

There may be a loose wire or the gauge or sending unit may be going bad. The first thing I would do is to hook up a temporary oil pressure gauge, not using the old one at all. With this watch gauge while driving and see what readings you get. If the readings still jump around you have a pump that is getting weak and failing, If that is the case the pump should be replaced, but with high milage you may consider rebuilding the entire engine. If the readings stay normal start checking for a loose wire at gauge or sender. Then check sender, then gauge and replace as needed.