In addition, WestCat has claimed that the fuel transition has led to a reduction in the maintenance required for emissions equipment and internal engine components.
The diesel is a low-carbon fuel that is said to be produced from 100% renewable and sustainable raw materials.
WestCat serves the cities of Pinole and Hercules, and unincorporated communities along the eastern edge of San Francisco Bay, operating a network of 14 fixed routes.
Jeremy Baines, vice president of Sales, Neste US, said: "Neste is happy to have a progressive transit agency like WestCat join the ranks of other front-runners in the quest towards more sustainable solutions. By making the switch to Neste My Renewable Diesel, they are committing to reducing emissions without compromising fleet performance."