Plus if you have the ability to turn arbitrary currency X into BTC, you can certainly change it into USD, which is far more stable than BTC. So, nope. This is not a good use for BTC.
With enough time passing you have an entire underground economy- conveniently denominated in dollars.
I'm guessing the friend sold the petrol for USD, right?
Zimbabwean who lived through this checking in - let me add context and help deconstruct this for HN: People (and banks) were converting Zimbabwean dollars to anything that could hold value and could be easily resold (in US Dollars) ASAP - this could be petrol or petrol vouchers, groceries, cookies - anything at all that could be bought with Zimbabwean dollars and flogged for USD. One of the retail banks got in trouble with the central bank after adding masonry bricks to their commodity portfolio[1]. Petrol was definitely a risky. Bitcoin would not have solved this because the using Zimbabwean dollars to purchase of commodities was only the first step to procuring US dollars while arbitrating the delta between the official exchange rate that formal businesses had to use, and the much higher real exchange rate as determined by the market. The hypothetical bitcoin:Zimbabwean dollar exchange rate in 2008 would have always tracked the market rate with no opportunity for arbitration.
1. Not brick futures or other fiscalised instrument: the bank bought and took possession of piles of bricks for resale later to hedge against inflation
His house was filled with petrol (gas) because he'd been paid and he had to buy something the same day that would keep for a month and hold it's value or his money would evaporate. So we sat in his house praying there wasn't a fire.
That's the use case for Bitcoin: currency of final resort. It's the same as gold only better (can't be faked, hard to steal etc).
I think in countries with stable currencies and after 2 decades of low interest and inflation, that's underrated as a use case...
I also believe (forgive the digression into my weird conspiracy theories) that one reason the US has made so much progress on legalised weed is because crypto and the dark web basically mean you can get whatever you want delivered right to your door. But that's just my own weird world view.