Some vehicles (BMW, Mercedes, some models of GM vehicles) do have a low oil level warning light. Most cars do not. However, once someone has an electronic marvel to perform tasks for them, this most likely strengthens the tendency to take a hands-off approach to things like manually checking the oil. Personally, I would not mind if my car had one of these specialized warning lights, but even if it did, I would still check the dipstick frequently. Over-reliance on electronic warning devices could be self-defeating in the long run, so there is nothing like the hands-on approach.
As to the info in your Owner’s Manual, you are reading something into it that is not there, but I will admit that it would be better if car manufacturs gave a technical explanation of exactly what the oil pressure warning light does and does not do. Let me take a whack at what I think Owner’s Manuals should say on the topic:
[i]If your Oil Pressure Warning Light comes on, immediately pull to the side of the road as soon as it is safe to do so, and shut off your engine. Check the oil level on your dipstick, and add oil, if necessary, in order to bring the oil level to the “full” mark on the dipstick. Be careful not to overfill the crankcase, as an oil level that is too high can be as damaging to an engine as an oil level that is too low.
Observe the engine and the ground underneath the engine for indications of an oil leak. If the oil level was low, after refilling to the full mark on the dipstick, restart the engine and see if the oil pressure warning light goes off. If it does go off, that is an indication that you had allowed your oil level to drop dangerously low–so low that the oil pump was not able to supply sufficient oil pressure to the extremely sensitive bearings and the cylinder walls in your engine.
The low oil pressure warning light will not come on until the oil level in the crankcase is severely depleted. The purpose of this light is to warn you of dangerously low oil pressure–not a low oil level–and should not be taken as a substitute for manually checking your oil dipstick very frequently. If the oil pressure warning light does not go off, that is an indication that your oil pump is still unable to supply sufficient pressure to the engine, and the engine should be immediately shut off. Have the car towed to the XXX dealership or a competent mechanic for diagnosis.
The oil pump may not be able to supply sufficient pressure for a multitude of reasons, including a build-up of sludge in your engine as a result of infrequent oil changes, or as a result of our defective design of the engine.[/i]
I am being somewhat facetious in the last sentence because no manufacturer is going to own up to defective design, but in reality, all too many car owners NEVER bother to read their Owner’s Manual, so no matter how detailed an explanation is provided, it may not do any good. However, something along the lines of what I wrote above would help to inform those who do bother to open their Owner’s Manual. Then, of course, there is the question of whether this little bit of extra information might be considered too technical by the “all I know is that I put gas in it and it runs” crowd.
In summary, I think that manufacturers could do a much better job of providing clear and complete information in their manuals, but the onus is still on car owners to actually read that information. Nothing in life is perfect, unfortunately.