Really? Your local price of gas at the pumps goes up and down by 10 cents/liter every week? Here in the US that would translate to 40 cents/gallon fluctuation every week, and if that were happening, it would be a major political crisis. While we in California pay more for gas than just about any other location in the USA, at least the fluctuation is usually slower than what you are putting up with.
I don't know how reliable the remaining mileage estimate is. Given all of the stuff we hear in the news about auto manufacturers cheating on emissions, it has occurred to me to wonder if they might also cheat on the fuel economy. A really easy way to do that might be to have the odometer report that you'd traveled a full mile or KM when you'd actually only traveled 90% of that distance. Does anyone actually check odometer accuracy? Seems to me like the manufacturer has multiple incentives to exaggerate mileage you've actually driven, and I have to wonder if anyone is looking over their shoulder in this respect.
But regardless of how accurate the odometer and the remaining mileage estimate is or isn't, I think it might be a mistake to push the envelope in this regard.
I used to live in a part of Maine where winter storms could bring local power outages that would last for days or maybe even more than a week. When that happened, not only was my house struggling to stay warm, but also I was struggling to find a gas station that had electricity to run the pumps. Now I live in southern California and I worry less about winter storms but more about earthquakes, fires, possibly evacuation orders, and how far I might be able to travel in congested traffic on short notice without having an opportunity to fill my tank. I try not to let my fuel gauge ever run lower than 1/4 of a tank because of that. When I consider how much I pay for insurance, buying gas on a day or at a place where the price is higher than I'm accustomed to still feels wrong, and I always prefer to take my business to the gas station with the best price, but paying a bit more at the pump to ensure that I am always prepared for emergencies feels cheap compared to what I pay for insurance.
2018 Niro PHEV Gravity Blue