California Air Resources Board

As of January 1, 2024, all fleets subject to the In-Use Off-Road Diesel-Fueled Fleets Regulation (Off-Road Regulation) are required to procure 99% renewable diesel (R99) or 100% renewable diesel (R100) for use in all vehicles subject to this regulation when operating in California. The Off-Road Regulation recognized the need for and provided potential renewable diesel fuel use exemptions due to cold weather.

There are two types of low temperature exemptions that provide flexibility to mitigate potential performance issues when using renewable diesel at cold temperatures. In both cases, the temperature threshold is 20 degrees Fahrenheit (20⁰ F), and both exemptions require additional reporting.

Cold Weather Exemptions

Winter low temperature (Section 2449(f)(2)(C)): From mid-October to February, off-road diesel vehicles are allowed to use conventional diesel if they are located or operated in areas where temperatures drop below 20°F in January.  Off-road fleets may use public or private weather station data and may use historical low-temperature data from the 10 years prior to the fleet requesting the use of this provision.

Intermittent low temperature (Section 2449.1(f)(2)(D)): This exemption allows off-road diesel vehicles to use conventional diesel during unexpected cold snaps when temperatures drop below 20°F, even outside of the usual winter months. Fleets can switch to conventional diesel if the weather forecast, within 14 days, predicts such cold weather. Forecasts from sources like the National Weather Service or weather apps are valid. Vehicles can use the remaining diesel in their tanks after the cold snap without needing to drain it.