I have no idea 
My baby hasn't either consistently loved or hated the car. He does seem to take issue with the car seat. He is 3 months old and trying to sit up whilst we are moving. it is at full recline which is not that reclined. choice for my car (volvo 360) was limited - we bought from and had it fitted at mamas and papas.
he seems to he developing a true hatred of it though, regardless of whether or not he has someone sat in the back with him. today he screamed from the second I put him in it, I stopped car after 15 mins as he was in such a state. he refused boob and only calmed down when I took him out of the car to show him some trees. the second I had it him back in seat he screamed and carried on after I retrieved the purple, sweaty mess from the back til he literally passed out on my shoulder 

is this normal/a phase?? any ideas on how to help him travel better??? burn the seat? burn the car??? never go anywhere again????