In the first seasons of Fringe, we see all of the Fringe division drive Fords. The series was sponsored by the Ford Motor Company at the time, as noted in the closing credits.
Peter was removed from the timeline at the start of season 4,
we see them driving Nissans — or so I noticed in S4E4 "Subject 9". And indeed, there was now a message acknowledging Nissan's sponsorship.
Is there an in-universe reason for that, or did they just switch sponsors?
The other changes caused by Peter's disappearance are very small and only related to the people he would otherwise have interacted with.
So why are they now driving Nissans instead of Fords? Is there an in-universe explanation?