The 2018 Volvo S90 is quite different from the 2017 – in that for 2018 it is only offered in the long wheelbase model which is 4.7 inches longer in total, and gives those sitting in the back seat 4.5 inches more leg room (this is also great for tall adults in front who want to put a large rear-facing car seat behind them and not have to scoot their front seat forward to accommodate). This extra leg room is also helpful for keeping forward-facing kids from kicking the back of the front seat. The 2018 S90 is great for 2 kids riding in back (one on either side) but consider 2C basically useless, for car seats or adults. 2C is quite different from the 2017 model – now the head restraint is fixed and sticks out a lot (not good for forward-facing seats, or driver visibility) – so you’ll want to keep 2C folded down to be the arm rest it was truly designed to be.
The S90 was reintroduced for 2017 – after having not been made since 1998. 2D and 2P are the same in this model year as for 2018 – but 2C is different. 2C has an exceptionally large bump (more like a ski slope) a the seat crack which will be very problematic – but visibility for the driver will be better in the 2017 as the center head restraint can be lowered – whereas for 2018 it is now elevated and obtrusive – and the only way to get it out of the driver’s view is to fold 2C down so it becomes an arm rest. Consider 2C to be a basically useless spot for most car seats – and even adults due to its narrow dimensions.