My oil light doesn't go out instantly.Have checked with a couple of other N/A owners and theirs too is the same.This is ONLY cold starting, when starting at other times it goes out straight away! I use 10/40w oil, changed at 3k intervals.
I work at Honda in Swindon, and this is not an uncommon thing.Our diesel civic......remember they are brand new......when started cold, take up to 4 secs to lose the oil light! I also had an MR2, that too took 1 to 2 secs for the light to go out, so if yours is similar, still get it checked but i wouldn't worry too much.
Can others, give it a go on a cold start, to compare?? Al.