If your car was damaged in a Coweta County car crash, your insurance company must pay to fix your vehicle. However, your insurance company is only obligated to have your car repaired to the condition it was in before the accident.
In the insurance world, putting new parts on old vehicles is considered "betterment." The insurance company believes that new parts make your car "better" than it was before the accident. For this reason, if a new part is used, the insurance company may not cover the entire cost of replacement.
Here is an example:
Your car had 40,000 miles on it when it was rear-ended in a Newnan car wreck. The accident damaged your muffler. The insurance company believes your muffler should have lasted 80,000 miles. Therefore, they are only willing to pay for 40,000 miles worth of muffler. This means that if you have a new muffler put on your vehicle, the insurance company may claim you are getting an extra 40,000 miles of muffler. The insurance company will then pay only half the cost.
You do have the right to only have original manufacturer parts used in your vehicle, but you may end up paying extra for those parts.