when you take Mochi out, where is he sitting? Hot Rod got sick whenever I had him in a carrier on the seat. Once I got the snoozer car seat for him he was fine. I think it is like people motion sickness, if you can see where you are going, you'll be okay. Maggie still gets motion sickness but I think she has finally figured out that if she goes to sleep, she won't get sick so now she immediately tries to snooze when she get in the car. It's funny, she'l like a lump all curled up in the carseat.
Good luck with your little one.