Use your legs, it is more healthy.
Do your way with your friends' car
and help them in other days.
As written in Wikipedia:
By having more people using one vehicle, carpooling reduces each person's travel costs such as fuel costs, tolls, and the stress of driving. Carpooling is also seen as a more environmentally friendly and sustainable way to travel as sharing journeys reduces carbon emissions, traffic congestion on the roads, and the need forparking spaces. Authorities often encourage carpooling, especially during high pollution periods and high fuel prices.
In 2009 carpooling represented 10% of commute travel in the United States,