Did the United States spend zero dollars on imported oil in 2020? No, that's not true: That would mean either that the United States did not import any oil in 2020 or that the oil it imported was free. Neither is correct.
The claim appeared in a Facebook post (archived here) published on January 30, 2021. The post read:
In 2008 we spent 400 billion on imported oil. Last year we spent zero.
This is what the post looked like at the time of writing:
(Source: Facebook screenshot taken on Mon Feb 22 23:38:14 2021 UTC)
For the claim to be true, either the United States did not import any oil in 2020 or the oil it imported was free.
Obviously, oil isn't free. Crude oil prices briefly traded below $0 in the spring of 2020, because of the global COVID-19 pandemic and a shortage of crude oil storage prices. That's not what consumers paid for gasoline and heating oil and crude prices quickly recovered and have since remained relatively flat. See here for a chart of crude oil prices over time. (Note that oil prices in 2008 hit an all-time high in the summer. Then, amid the global financial crisis, prices plummeted.)
It's also not true that the United States did not import any oil in 2020. Not including December, which hasn't been reported yet, U.S. imports of crude oil and petroleum products topped 2.5 million (in thousand barrels), according to data from the U.S. Energy Information Administration (EIA). By comparison, U.S. imports of crude oil and petroleum products in 2008 were around 4.7 million (in thousand barrels), EIA data shows:
(Source: EIA.org screenshot taken Mon Feb 22 11:01 UTC 2021)
The post may have confused imports with net imports, which is defined as imports minus exports.
When you look at EIA data for net imports of crude oil and petroleum products in 2020, it shows negative numbers for most months. For the first time, the United States is thought to have exported more petroleum than it imported for the year. Still, that fact doesn't mean there were no imports, nor does it mean that the country spent zero dollars on imported oil. It just means that exports exceeded imports.