Once the light comes on,there is a code.
The computer will remember it.

 Being low on oil will not turn on the engine light.

Sorry but incorrect.  The codes (if any) are stored in the memory of the ECM
and can still be read.  If you go 50 start cycles without the light coming
back on, or if you pull the fuse to the ECM for 3-5 minutes, or if you
disconnect or change your battery this will also clear the codes.

You gave us only four pieces of information (1993, 350 engine, auto tranny,
uses oil) and based on only these four things there is absolutely no way
anyone could even remotely tell you why your SES light is coming on over the
internet without either guessing or much more information.  Plain and simple
you need to pull the codes and have someone do some practical diagnostic
work on it.  The codes will only tell you what the engine senses is wrong
but may not tell you exactly what is broken.

But if you are still looking for something specific as the cause, I think
it's the power windows.  It does have power windows, doesn't it?

Cheers - Jonathan