I have seen ideas on this subject in the past but do not recall seeing a simple low level light.

Your device is a more accurate solution than the stock pressure gauge.
It should give a broader range of the actual pressure than the one on the dash that gives us 3 bars or about half of the actual oil pressure.
And it seems illogical for the stock gauge to show full pressure when there is in fact zero pressure.

In regards to to ferrule crimp: I went to CarQuest and they said that the metal portion of the line would not fit into their machine. The first three guys at NAPA said the same thing and that their machine was the same as CarQuest and had the same fittings. But the next man that saw the hose, took it immediately to the back, cut off the old ferrules saw that the length of the metal line was long enough and had a flare at the end so that the high pressure line and steel ferrule that is used for air conditioning systems would work. He used a hand operated crimping machine and carefully applied pressure several times over many minuets and connection seems very solid.
$8.50 total
The factory upper hose was $127.80
I will report back after 1,000 miles.
A Mercedes shop in the next town uses this method exclusively for years. The operator of the machine is the key.
Ultimately it was the crimp that failed on the lower old oil cooler line that caused the biggest oil lose. The oil was actually misting out and was visible on top of the hood and cowl in front of the windshield. Could not have seen it but for the fact that the car is white.
I hope that this one last half as long as the old one.

I missed the Low Oil Level part.
I have seen none for the 617 or 616 Engines.

Some of the later Mercedes Diesels have the Low Oil Level indicator. However, that does not solve the issue either. If something happens and the Oil Pump does not work you Oil Pressure will stop but you will still be full of Oil.

From what I have read more Members have had loss of Oil Pressure from the Hoses leaking than from the Oil Pump not putting out pressure. So it is possible that a Low Oil Level Indicator would be a good idea if someone would come up with a way to retrofit one to the older Engines.

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84 300D, 82 Volvo 244Gl Diesel

Low oil level and low oil pressure warning do different things, and both good to have. Low oil level warning would have saved the OP from his problems.

VW uses a probe (not a float switch type) to measure coolant level (by measuring the coolant's conductivity). I was hoping that I can measure the conductivity of the carbon soot loaded diesel oil. I know oil is non conductive but carbon is and was hoping the soot would make the oil conductive which would make a low oil level probe much easier to retrofit into the oil pan. Unfortunately a test I did on some used diesel oil found it non conductive.

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85 300D turbo pristine w 157k when purchased 167,870 July 2025
83 300 D turbo 297K runs great. SOLD!
83 240D 4 spd manual- parted out then junked