It's common for babies to love sleeping in the car seat, and while there's no harm in it for now, your baby should learn to go down in his crib. (After all, he will outgrow the car seat eventually.) Try to figure out why your baby prefers his car seat. Some babies feel more secure sleeping in small, cozy spaces, and maybe yours is one of them. Perhaps the seat has a soothing rock that helps him nod off. Sometimes, babies develop a dislike for their own beds because the firm mattress feels cooler and harder than their car seat. Or it could be that your baby hates lying flat in his crib, which is especially common for infants with bad reflux.
To help your baby become a fan of his crib, start by placing the car seat in the crib during bedtime for about a week or so, so he can get used to the new sights and sounds of his nursery. You should also put him down for naps in the crib so he can test it for short periods of time. Warming up his sheets with a hairdryer for a minute beforehand may help the crib seem more comfy (be sure to feel it first to make sure it's not too hot). If you suspect it's lying flat that's causing the problem, you can try propping up your baby's head slightly by sticking a small wedge under the crib mattress. Remember, you should never use pillows or extra blankets in the crib, which can raise your baby's risk of SIDS (sudden infant death syndrome).
Once your baby's adjusted to napping without the car seat, you can stop using it at night too.