We went to the party with our car.
We went to the party by car.
We went to the party in our car.
Use by + means of transport to say how you travel: ‘by car’, ‘by bus’, ‘by train’, ‘by plane’ and ‘by ferry’. Do not use an article in these expressions.
When talking about a particular car, use in: ‘in our car’, ‘in the car’. We also use in with taxis and vans.
Use on with buses, coaches, trains, trams, planes, ships and ferries: ‘on the bus’, ‘on a train’, ‘on a plane’, ‘on a ship’. We also say ‘on a bicycle’ and ‘on a motorbike’.
Say ‘get in a car’ and ‘get out of a car’, but ‘get on a bus’ and ‘get off a bus’. The same applies to trains, planes, ships and ferries.