642 cannot be considered a ‘Great’ credit score but it is a ‘Fair’ score. 

You can get a car loan even though your credit score is lower than 650. It's not impossible, but it's a little disadvantageous for you. It's up to the bank's discretion to lend you the money. However, you might get unfavourable conditions with respect to the interest rates and other loan benefits in a car loan with such a low credit score.

How to improve my 642 credit score?

You can follow a few simple steps to improve your credit score upward of 642:

  1. Do not go over 30% of your credit limit: Not only should you never reach your credit cap, but you should also never exceed 30% of the limit. Consistently spending more than 30% of your income indicates that you have a problem with budgetary restraint and do not have enough money left over to meet your repayment obligations.
  2. Make on-time and full payments: Making on-time and full payments is one of the easiest ways to keep a strong credit score and history. Try to pay off your monthly credit card bill in full and on time; this single move would have a significant positive effect on your credit score.
  3. Applying for several cards in a short period of time is not a good idea: If you apply for too many credit cards in a short period of time, lenders may think you're 'hungry' for credit. Your credit score will suffer if you submit too many applications without receiving subsequent approvals.