Cars 2: The Video Game

I found this easier playing a single player free play map, doesn't matter which, with 10 players, and easy difficulty. At the start of the race, find Mater and draft behind him, tapping the throttle. He is slow and very predictable. I received the achievement in about 2 laps.

First off Drafting is when you drive directly behind another car. There will be an indicator on the bottom right hand corner if you have done it correctly.

I found this easiest by using 2 controllers on a normal race (you can also cut back # of AI players but it won't matter much. Note:I think its a lot easier to pick 2 of the same character so their stats are the same.

Once the race starts simply let all AI players pass you, then take controller 2 and run him along side the wall angled slightly towards it and leave him there while you put player 1 (the one going for the achievement) directly behind him. Once this is done start holding the RT button on both controllers (make sure it says drafting in the bottom right hand corner of player 1's screen) and keep them as close together as possible. The game gives you a little leeway. If the cars end up separated either reposition them or restart (the game will save any progress made towards the achievement.

You can track your progress in the Awards section on the main menu under Crest.

Obviously this is even easier with 2 people but I didn't have that luxury.

I'd just like to add to the other solutions.
I was having a ton of trouble getting this and couldn't use two controllers, took too long.
So what I did was start up a race on easy, do nine laps with ten cars. If you stay between 6-8 position the racers usually drive pretty slow and are very predictable, they will follow the same path every lap, just get close enough to draft them.
If you're too close to the front the drivers are quicker and swerve all over the place, and with the last place drivers; well they are just way too slow.