Why do you expect the loco to pull all the add on cars at once.
Lionel sells lots of additional PE cars you can "add on" to the original set, if and as you like any add on set. As far as I know, the loco will pull any add on car set and the original set.
However, where did you see them claim, and frankly why do you expect, that it will pull all of the add on sets in addition to that original set together? I think that is a very unrealistic expectation. Lionel offers lots of different PE add on sets to give people a diversity of different options. They never represented that a single loco will pull them all. Why not buy another loco, then either pull a longer train, or run two trains?
