Omitting a Conjunction in a Series

After doing the sentence error exercise, I've learned a new rule that I thought I would say a little more about. This is number seven on the sample questions page:

They said they plan to sleep in their SUV, a five-year-old Chevy Tahoe, into which they’ve packed boxes of important documents, bags of clothes, some food

I mistakenly added the word "and" between the serial comma and the last item in the series, which is actually unnecessary. Below is an excerpt from the ClearWriter website.

"Dropping a conjunction has the opposite effect of adding a conjunction: creating a series that is not exhaustive, but a mere sampling of possibilities. It also makes your reader see the parts of the series as more separate than joined.

This 20th century is baffling, difficult, paradoxical, revolutionary."

:)