Sure, there is 55 gallons in a barrel. $4 x 55 = $220. The post said OIL to reach $4.00 per gallon.
An oilfield barrel is 42 gallons.
There is also a refining margin to account for. A barrel of raw oil does not make 42 gallons of gasoline and it costs money to refine and transport. You of course can’t do that without buying a refinery and trucks and such.
A better approximation is the current price of gasoline / the current price of oil = $/gallon of gasoline / $/barrel of oil.
e.g. $2.89/gallon / $91.00 / barrell = 0.03186 gasoline / barrel
Then $4.00 gasoline / 0.03176 = about $125/barrell oil
Oil will not reach $4.00 per gallon. I believe the title of the article was “Who, How and Why: $140 Oil and $5 gas”
The profit margin on gasoline goes down when oil price goes us since refiners try to offset the lack of demand to keep the refineries running optimally and also a result of them getting caught with lower priced contracts vs. spot oil prices.