This Achievement (like the 16,000 KM / 10,000 Miles Driven Achievement and the 1,600 KM / 1,000 Miles Driven Achievement) can be obtained through Story Mode (through the Main Races) (Offline).
This Achievement (like the other ones mentioned above) is Cummulative, therefore, it can be obtained Offline or Online (or both), Multi-Player / Split-Screen also counts towards this Achievement.