metrompg.com series | Highlighted on Fuelcons
Between 2005 and 2009, Darin, the host of metrompg.com, shared some of his experiments on his vehicle’s fuel consumption on…metrompg.com!
Each individual post includes an introduction, a description of the conducted experiments and their results, as well as a discussion. Although the data is somewhat older, it still holds relevance, at least in terms of conventional vehicle fuel consumption.
Fuelcons plans to feature these experiments in a “metrompg.com series,” starting with this study on the adverse impact of a roof rack on fuel consumption.
The experiment aimed to assess the effect of a roof rack on a vehicle’s fuel efficiency. Inspired by the sight of numerous vehicles equipped with roof racks at a ski hill parking lot, Darin sought to measure the extent of the fuel efficiency reduction caused by these additions. The experiment involved comparing three conditions: driving without a roof rack, driving with an empty roof rack, and driving with a mountain bike secured to the roof rack.
The results clearly demonstrated a direct link between the presence of a roof rack and decreased fuel efficiency. Without a roof rack, the average fuel economy was 55.2 miles per gallon (MPG [US], equivalent to 4.25 L/100 km). Adding an empty roof rack led to a decline in fuel economy, averaging 48.2 MPG (4.88 L/100 km). As anticipated, placing a mountain bike on the roof rack caused a further substantial drop in fuel economy, with an average of 40.1 MPG (5.87 L/100 km). Additionally, Darin noted that the increased aerodynamic drag resulting from the mountain bike on the roof rack was immediately noticeable through the engine’s behavior.
This experiment underscores the significance of aerodynamics in relation to fuel efficiency, highlighting the considerable impact of roof racks on mileage. Consequently, the study concluded that the fuel economy penalty associated with roof racks could be substantial, urging drivers to be mindful of their presence, especially when not in use.
Source: metrompg.com
Comment:
The inclusion of the mountain bike on the rack reduced the mileage from 55.2 MPG to 40.1 MPG, marking a decrease of 27.3%. When considering fuel consumption in L/100 km, the consumption rate increased from 4.25 L/100 km to 5.87 L/100 km, a rise of 38.1%. While the latter calculation seems to be more pertinent for gauging relative changes in actual fuel consumption, these varying readings have been previously discussed in the article titled “The MPG Illusion”, which is also summarized here.