uh, yeah, i do live in a condo. the condo reg's that most boards use is usually a generic one (i am told by the property manager) and it will expressly prohibit the performance of maintenance on you vehicle.
again, the reason for this is to prevent people from doing things like oil changes etc. which in turn is because underground parking is an exclusive use common element. they don't want oil stains, contamination, slips and spills on the oil, etc.
just because you got away with it, doesn't mean it's actually allowed by the board.
and it's not just the security staff that you'd have to be concerned about: other residents may have an issue with you doing that stuff in the parking garage too and file a complaint, to which the property manager will have to respond. penalties can range from warnings to fines that will be levied against your common element fees. the property manager in my building is a stickler. he does his own patrols too to make sure the security and cleaning staff are doing their job.
my post was in response to people who stated that the OP should have just done the oil change in his own garage. it's not that simple, so there are good reasons for the OP not doing so.