As if to top off a night already characterised by drunken decadence and mad partying, Nick describes the scene that greets him as he leaves the party, and makes him realise that "the evening was not quite over." He sees lots of headlights and a car in a ditch which has lost its wheel. Owl-Eyes has exited this crashed car and is standing in a drunken stupor, contemplating the car and finding it an amazing site. In response to questions about what has happened, he says "I know nothing about mechanics." In response to further questions he reveals that he was not driving, and the crowd looks upon another man who gets out of the car, likewise clearly drunk, asking if the car had run out of gas, and then asking where the nearest petrol station is.
Nick is clearly confirming our impressions by showing us this incident of two men who, in an era of Prohibition, are so drunk that they crash a car and show a complete inability of understanding what had actually happened. The link of decadence and illegal drinking to Gatsby's parties is thus cemented.