Changes

Take metro line 3 to "Mortensrud" and get off at the last station, then cross the bridge over metro track and walk for about 300 meters. You will enter petrol station on motorway E6. Either ask drivers there, hitchhike on the busstop on the motorway just 100 meters next to the gasstation, on the onramp itself, or on the busstop before the onramp. Basically just go there and find your favorite way to find a ride going south.

You may want to try Esso petrol station (diesel is cheaper there so lots of people fills up there and other advantage is there is a MC D. right next to it). To get there, take subway to Hellerud, turn right into Smalvollveien and walk till you get to Esso. Some might find useful to know that there seem to be fewer ticket controls on that line.