Full list of all 36 NASCAR '15 achievements worth 1,000 gamerscore. It takes around 15-20 hours to unlock all of the achievements on Xbox 360.
You passed a total of 250 cars
You won a race after Qualifying first and leading the most laps
You won a race while driving a Chevy
You invested in all areas of the Race Shop
You won a Career race using only refurbished parts for your car
You created a custom scheme in the Paint Booth
You won the All-Star Race
You signed 10 sponsors to your car
Make it to pit road with a flat tire
Win a race with the HUD turned off
Start and finish a race without any driving assists
Drive as 10 different drivers
Run a custom tuning setup in a race
Be the Lucky Dog driver in a race
Be involved in a wreck at Talladega
Qualify on Pole 20 times
DNF from a race by critically damaging your car
Win a race while driving a Ford
Win a race while driving a Toyota
Research everything in the R&D department
Win the Sprint Cup in Career
Win the Sprint Cup in Career on at least 90% difficulty
Finish your first Sprint Cup Season in Career
Win a League Season
Take part in an Online Race
Win your first Online Race
Win 10 Online Races
Win 20 Online Races
Participate in 50 Online Races
Participate in 100 Online Races
Save an Online Replay
Make a custom brush in the Paint Booth
Take a picture using Photo Mode
Win the Sprint Cup in Chase Mode
Win the Sprint Cup in Single Season Mode
Run 10 laps in a single Track Testing session