The only time I have had an oil light on is when I parked up a steep incline with the nose facing down.
When it levels out the light goes off.
Your oil light is on for a reason, no oil or faulty switch.
It is something you really shouldn't ignore.
i was just curious what oils people use in their D22s in general as i am tempted to use 5w30 in my next service, and was wondering if you had 5w30 when u got the oil light...