Many factors affect the vehicular fuel consumption rate. The most significant traffic-related ones are speed, number of stops, speed noise, and acceleration noise (acceleration standard deviation). Fuel consumption models for both urban and highway traffic are used to evaluate the effect of these factors. Previous literature shows the speed and the acceleration of vehicles as well as the aerodynamic effects are the most commonly used variables in the highway fuel consumption mo dels. However, most existing models are based on the average or cruising speed and the effect of speed variation is by-and-large ignored. Incorporating the speed noise as a variable in the prediction models seems impractical because measuring it is cumbersome. However, knowing the relation between speed and speed noise may allow including the effect of speed noise in the model indirectly. To that end, this study examines the relation between speed and speed noise. The resulting mathematical relation is used to incorporate the speed noise effects in the fuel consumption model.