Selecting the correct fuel for your backup power system is the single most important maintenance decision a homeowner or business owner can make. When the grid fails, a Generac generator is designed to activate automatically, but only if it contains the specific formulation required for optimal combustion. Using the wrong grade can lead to poor performance, engine damage, or a failure to start when you need it most.
Understanding Standard Premium Gasoline
For the vast majority of residential installations, a Generac generator requires unleaded gasoline with an octane rating of 87 or higher. This is the same fuel you put in your primary vehicle, making refueling straightforward. It is crucial that this gasoline is fresh; fuel left in a storage tank for more than 30 days can begin to degrade and form varnish-like deposits.
Ethanol blends, specifically E10 (10% ethanol), are generally acceptable for short-term use. However, manufacturers recommend avoiding fuels with higher ethanol concentrations, such as E15 or E85, unless the engine is specifically designed to handle them. Ethanol absorbs moisture from the air, which can cause phase separation in the fuel tank. This separation creates a layer of water at the bottom of the tank, which is highly corrosive to the fuel system and can prevent the engine from starting.
The Critical Role of Fuel Stabilizer
Extending Shelf Life
To combat the natural degradation of gasoline, using a fuel stabilizer is a highly recommended practice. If you plan to use your generator infrequently—such as for seasonal testing or emergency backup—stabilizer prevents the fuel from breaking down into a gummy substance that clogs injectors and filters.
When adding stabilizer, pour it into a portable gas can filled halfway with fresh fuel. Shake the can vigorously to ensure proper mixing before filling the generator’s tank. This proactive step can extend the usable life of the fuel for up to 12 months, ensuring your unit is ready for instant operation.
Diesel vs. Propane Alternatives
Diesel Fuel Capabilities
While gasoline is the standard, some models in the Generac lineup are engineered to run on diesel. Diesel engines are known for their durability and fuel efficiency, making them a popular choice for commercial applications or homes in rural areas where diesel is readily available. If your unit is a diesel model, it will be clearly marked, and you must use Number 2 diesel fuel.
Propane as a Viable Option
Generac also manufactures dual-fuel and tri-fuel generators that offer the flexibility of natural gas or propane. Propane is an excellent alternative for users who want a longer shelf life and a cleaner burn. Similar to gasoline models, you must ensure the unit is configured for propane and that you have an adequately sized tank to support the kilowatt load you intend to power.
