Yes, your motor is a 119.975
What is the mileage of your 93 400e?
Can you give us a better description of what you mean by "low" oil pressure? Does the oil pressure rise to "highest" level on the indicator when you accelerate? At idle, does the pressure go below the lowest mark? Does the oil pressure change as you car reaches operating temp?
I use Mobil 1 15w 50 Synthetic in Summer months, and Mobil 1 5w 50 during the winter.
I have a subscription to
www.alldatadiy.com . It’s an online manual service with an annual fee of $24. per year for the 1st car and $14 per year for any additional car.
Failure of the oil pressure sending unit is not unusual on the older M119 with high mileage engines. You will find the oil pressure sending unit at the base of the oil filter housing. Since I’ve never experienced a failure of the oil pressure sending unit, I can’t comment on how the units begin to fail. Since the units work off resistance/ohms I’m unsure what you are describing is characteristic of a failure. If you check the unit, if you notice it leaking oil from the oil pressure sending unit plug - change it out.
One might suspect the oil guides under the valve cover have come loose causing low oil pressure at idle. Does your engine produce a distinct “ticking” also known as hydraulic lifter ticking noise. I think your model engine has the medal oiler tubes and should not suffer the failure the same as the plastic ones. Maybe someone else can comment?
To replace "low oil level sensor" would require you to remove the oil slump...check the switch with a multi meter. If the ohms between the switch and ground read above .10 ohms – replace the switch. Otherwise check the wiring for continuity.
Hope this helps...