Harley-Davidson and Yamaha are two of the most renowned motorcycle brands in the United States, each offering a range of models with varying fuel efficiency. When comparing fuel efficiency, Yamaha generally outperforms Harley-Davidson. This is primarily due to Yamaha's focus on producing lightweight, aerodynamic motorcycles with advanced fuel-injection systems.

Yamaha's motorcycles, especially their sport and adventure models, are known for their high fuel efficiency. For instance, the Yamaha R1, a sportbike, offers an impressive fuel economy of around 45 miles per gallon (mpg) on the highway. This is significantly higher than the average highway mpg of Harley-Davidson's touring models, which typically range from 30 to 40 mpg. The Yamaha FJ1200, a popular adventure tourer, achieves an estimated 45 mpg as well, further highlighting Yamaha's commitment to fuel efficiency.

The reason for Yamaha's superior fuel efficiency lies in their engineering approach. Yamaha motorcycles are designed with lightweight materials and aerodynamic shapes, which reduce drag and improve fuel economy. Additionally, Yamaha's fuel-injection systems are highly efficient, ensuring optimal combustion and minimizing waste. These systems are calibrated to deliver the best possible fuel economy without compromising performance.

Harley-Davidson, on the other hand, has traditionally focused on providing a unique riding experience with their classic and custom motorcycles. While they have made strides in improving fuel efficiency, their models often weigh more and have less aerodynamic designs compared to Yamaha's offerings. This results in lower fuel economy, particularly in their heavier touring and custom models.

It is important to note that fuel efficiency can vary within each brand, depending on the specific model and its configuration. For example, Harley-Davidson's Sportster line offers more fuel-efficient models compared to their heavier touring bikes. However, overall, Yamaha's commitment to lightweight design and advanced technology makes them the more fuel-efficient choice for most riders.

In conclusion, Yamaha motorcycles are generally more fuel-efficient than Harley-Davidson models. This is due to Yamaha's focus on lightweight design, aerodynamics, and advanced fuel-injection systems. While Harley-Davidson offers a unique riding experience, their models often have lower fuel economy, making Yamaha the more fuel-efficient choice for many riders.