We are yet to see if this can be achieved after the servers are turned off. If you want to make sure you get it before then, and you only have a couple of hundred miles to go, then you can get this in a few hours by:
1) Choose time trial, and choose the second-to-last track in India
2) Choose a fast car - I used the Aston Martin Vanquish
3) Use a rubber band to hold down
4) Leave the console on for a few hours
This track in India is good for resetting you onto the tarmac quickly and not letting you get stuck; you can also get a fair speed up at times which is needed to collect the miles.
You can check how many miles you have done in total by looking at your profile, statistics and progression. Note that is the total miles you've driven, and if you drove lots before joining a club you'll have to go over this number.