General aviation is approaching one of its most significant fuel changes in decades, as the industry works to replace 100LL, the leaded aviation gasoline used by thousands of piston-engine aircraft across the US. The transition is driven by public health concerns and a federal target of eliminating leaded avgas by 2030, but the challenge extends beyond developing a suitable replacement. Fuel prices, aircraft approvals, distribution networks, and operating budgets will determine how quickly pilots can adapt.For aircraft owners, the numbers reveal a complicated picture. An unleaded fuel that costs less than a dollar more per gallon might appear manageable, yet that difference can add thousands of dollars to an annual flying budget. Meanwhile, approval costs, the uncertain pace of nationwide distribution, and competing fuel formulations introduce additional variables. Understanding these calculations helps explain why replacing leaded avgas is becoming an economic issue as much as an engineering challenge.