Sab's right, there are girls out there who like cars
I have to agree with everyone on here, she doesn't seem to want to make the effort. It maybe expensive for her to come and see you but if she really wanted to then she would. I pay on average £200 for a flight every month to go down and see Neil and I'm a student with a lowly paid part time job. If its something you want then you find the money no matter what.
It will be hard cause you've been with her for a long time but she should love you for who you are and not what hobbies you have. Big deal if you're into cars, she surely has her own hobbies which you dont particularly like?
Keep your chin up though cause things happen for a reason.