Carmax is a terrible place to buy a car. They are overpriced and a dumping ground for people looking for an easy way to get rid of bad cars.

This should give you an idea of things to look out for:

https://www.carcomplaints.com/Ford/Mustang/2014/

If it has a manual transmission there have been a lot of problems reported, though I'm not sure if this applies to six-cylinder models or just V8s:

https://www.autoweek.com/news/industry-news/a32837939/ford-mustang-six-speed-manual-getrag-lawsuit/

Be sure to have a good mechanic give any vehicle you are considering a thorough pre-purchase inspection.

• I have a 2014 ford mustang and I am the second owner.
• The person who owned it before me they had some modifications on the vehicle like a cold air intake and the car was"sport tuned", they said.
• I was returned the car for 2 months and the RPM'S kept jumping and the car would thrown itself up to 7,000 RPM, when I was driving at 40-60mph they told me it was a dash/cluster issues,and they had the car for 8 month and left with with a rental, once I got my car back my transmission when out, and I'm currently paying tons of money for something they should have seen while working on the car...
• What should I do? I took a loan out for the new transmission and am currently making payments on both loans. It's my first "new car"