I noticed a couple of threads with similar problem during search, but some responses seemed to say that the issue was serious and some said otherwise so I figured it might depend on specific situation.

I have a 2004 A4 3.0L that I bought a year ago, and changed the oil about half a year after I bought the car (because I had no idea what kind of oil the guy before me was using, and wanted to be safe). I got the recommended 5W40 Synthetic Oil at Valvoline (Receipt calls it 5W40PBEXG). Now, a little over 3000 miles after the oil change, my "Min Oil" light came on, the light is yellow - I heard that most serious problems are reported in red. I'm confused, since the manual said I only need to change oil every 10k miles as long as I use Synthetic, but other threads suggest adding a bit of oil inbetween changes.

Additionally, I have no time to change the oil today and will need to drive about 30 miles. Is that a big deal? Can I drive that before adding more oil?

 

That just means the level is low, which means you are using or leaking oil. Whether its safe to drive depends on how low it actually is. Check the oil, if it shows up on the dipstick it wont hurt anything. You dont have to change the oil though, you can just add more of the same to it.

 

I just looked under my car, the ground is somewhat wet (I touched it, and it looked like oil) and the cover under my hood looks like it has oil on it too. This definitely looks like an oil leak, but why would it occur all of a sudden if I got my oil changed half a year ago and that problem didn't turn up until now?

 

a part probably failed. could be a crankcase breather, or could be a valve cover gasket, or could be a head gasket. lots of things....

 

get it in the air and checked out , it could be as simple as an oil filter or plug being loose or as bad as a cracked pan or leaking head etc...

 

Problem solved, it was a dented/cracked oil filter. No idea how it happened, when they were fixing my washer fluid tank+bumper a couple months ago the filter was fine.