No, you should not attempt to start a car with 25-year-old gasoline. Doing so will almost certainly cause significant and expensive damage to the engine's fuel system. Gasoline degrades over time, losing its combustibility and turning into a corrosive sludge that can clog fuel injectors, ruin the fuel pump, and damage the engine internals. The risks far outweigh any potential benefit of trying to start the engine without a proper fuel system flush and service.
Gasoline begins to degrade significantly within just a few months. After 25 years, the volatile compounds that make it flammable have evaporated, a process called volatilization. What remains is a thick, varnish-like substance. Furthermore, if the gasoline is an ethanol-blend (common since the 1990s), it's even worse. Ethanol absorbs water from the air (hygroscopic), leading to phase separation where water and ethanol sink to the bottom of the tank, causing rust and corrosion.
Here’s a breakdown of the primary risks and potential costs:
| Component at Risk | Likely Consequence of Using Old Gas | Estimated Repair Cost (Parts & Labor) |
|---|
| Fuel Filter | Clogged immediately, preventing fuel flow. | $100 - $250 |
| Fuel Pump | Overworked and burned out trying to push sludge; can fail catastrophically. | $500 - $1,200 |
| Fuel Injectors | Clogged with varnish, requiring professional cleaning or replacement. | $300 - $800 |
| Fuel Lines & Tank | Corroded and contaminated with rust and sediment. | $200 - $1,500+ (tank replacement) |
| Engine | Poor combustion can lead to hydro-lock (if water is present) or carbon buildup. | Potentially thousands |
The correct procedure is to siphon out all the old gas safely and dispose of it as hazardous waste. Then, the entire fuel system—tank, lines, filter, and injectors—needs to be professionally cleaned. Only after this extensive service should you add fresh gasoline and attempt to start the engine. For a vehicle that has been sitting for decades, a full mechanical inspection is essential before attempting to drive it.
