What Happens When Fresh Gasoline Mixes with Old Gasoline?
Blending fresh gasoline with old fuel is a common practice, especially in various storage scenarios. However, questions arise about the effectiveness and safety of this practice. This article explores the potential issues and outcomes of mixing fresh gasoline with old fuel, drawing on insights from storage conditions and industry knowledge.
Case Study: Mixing in a Boat's Fuel Tank
A few years ago, the author of this article acquired a boat that had been in storage for five years. The fuel had been treated with an additive before storage, but it still faced significant issues. One tank experienced phase separation, necessitating its discard. The other tank experienced rough idling, which improved only slightly after filling with fresh gas. Despite these challenges, the motive was to assess whether mixing fresh gasoline with old fuel could result in a usable solution.
The author, after owning multiple boats, recognized that topping off the tanks in spring with freshly mixed gas typically resulted in no significant issues. This casual observation forms the basis for a more generalized approach to the problem, acknowledging that the dilution rate and the condition of the old fuel are critical factors.
Understanding Phase Separation and Old Fuel Contamination
Phase separation and old fuel contamination, specifically, can pose significant challenges. When the fuel begins to separate into layers, with a visible layer of water or solid particles, it signals a problematic condition. Even a relatively low concentration of old, deteriorated fuel in new gasoline can cause erratic performance.
For instance, if you mix just a cup or two of old fuel with a 5-gallon container of fresh gas, the resulting mixture may still be usable. However, this is by no means a guarantee, and it is crucial to consider the specific condition of the old fuel. Contaminated fuel can lead to the formation of varnish, which accumulates over time on the surfaces of fuel containers and fuel delivery systems. This varnish can cause blockages and performance issues, particularly in older fuel systems.
Hydrocarbons and Their Impact on Performance
Gasoline is a complex mixture of hydrocarbons of varying molecular lengths, produced through the distillation of crude oil. Additives are often included to enhance certain properties, such as minimizing varnish formation and preventing phase separation. However, these components can adhere to fuel system surfaces over time, especially if the fuel is stored for extended periods. This adhesion does not affect the fuel directly but can create issues when the tank is refilled.
The lighter, more volatile components of gasoline can evaporate over time, leading to a potential change in the octane rating. However, this effect is generally minimal and does not significantly impact the overall performance of the fuel. The primary concern lies in the potential for contamination and the formation of varnish or sediment, which can block fuel filters and injectors.
Preventing Contamination and Ensuring Safe Use
If you suspect that your fuel might contain contaminants such as water or solid particles, it is essential not to mix fresh gasoline with it. Instead, it is best to discard the old fuel and start fresh. However, if the old fuel appears in good condition and does not contain visible water or particles, it is still advisable to mix it cautiously. A dilution rate of up to 2.5 old fuel to fresh fuel is generally considered safe but must be closely monitored for performance issues.
To prevent problems with both storage and in-car fuel systems, it is recommended to use fuel stabilizers and additives specifically designed for long-term storage. These products can help maintain the quality of the fuel and prevent the formation of varnish. Additionally, ensuring that the fuel cap is tightly sealed can minimize the evaporation of lighter, more volatile components.
Best Practices for Fuel Storage
For the safest and most effective fuel storage, it is recommended to top off the fuel tank when refilling, as this minimizes the amount of air exposure and the potential for contaminants. Regularly running the engine can also help circulate the fuel and prevent the formation of varnish. If you are storing fuel long-term, always use fuel stabilizers and clean fuel filters regularly.
In conclusion, while mixing fresh gasoline with old fuel can sometimes work, it is crucial to consider the condition of the old fuel and take precautions to ensure safe and reliable performance. Understanding the properties of gasoline and the risks associated with long-term storage can help prevent potential issues and maintain the efficiency of your vehicle's fuel system.