Earn 20 perfect Drafting scores.
When your vehicle is trailing another car at high enough speed, you can increase your speed efficiently by lining up behind them and benefiting from their efforts. Drafting requires that you be moving at least 70 mph, and the faster you are moving the further away from the lead vehicle you can be. To obtain a Perfect rating on a draft merely requires time. The longer you draft a vehicle, the more likely you are to obtain a Perfect rating. There are some caveats: You can't touch another car or the wall, and you can't leave the track.
Drafting generally doesn't work on corners due to the aerodynamics involved, but there are many straightaways in the game where it can be easily earned. It is quite likely that you will earn this without any conscious effort on your part. To increase your likelihood of getting a Perfect draft rating, stay on or near the racing line while on straightaways. You will need to be in sight of and behind another vehicle, preferably within 1-200 yards.
This can also be easily boosted with another player or a Drivatar in a private 1x1 match on Yas Marina full circuit or Road Atlanta full circuit. Whoever is getting the achievement will need to stay in second place and trail the other vehicle. At each straightaway you should then get a rating of Perfect Draft at least once, and on the longer straightaways multiple times.
The achievement will pop at the end of the race in which you earn your 20th. You can track your progress both in the achievement screen and in the stats menu of your player profile in-game.