It would take more space if the title was stored each time in the vehicle page instead of having it once in a separate table.
There is often more than one vehicle in a episode.
It is not only for the space taken, but also to keep the database structure somewhat clean and coherent (it is already not perfect currently).

Yes, makes take space. And I could have a make list separated to not have to reenter it each time. Same for models actually. This is one of the improvements that I may do one day.

For info:

cars table = 7.9 MB
comments table = 34.4 MB
movies table = 1.5 MB
users table = 0.3 MB

total = 44.1 MB
max allowed = 50 MB

If the database reaches the max allowed size, OVH (where the site is hosted) will put it on another server, which is slower.
I could split the database and put comments & users in a separate database, but some day we will reach that limit.