Study: That Roof Rack Is Killing Your Fuel Economy
Berkeley Lab research says it cost 100 million gallons of gas in 2015
That roof rack you absolutely had to have may come in handy now and again, but a new study from Berkeley Lab says that it's also costing you quite a bit of money in lost fuel economy. The cumulative losses are for the first time being measured on a national scale; on passenger vehicles it could reduce efficiency by up to 25 percent, and in 2015 these losses accounted for 0.8 percent of all national fuel consumption—that's 100 million gallons of gas lost because of added drag.
Berkeley Lab researcher Alan Meier, aided by Yuche Chen from the National Renewable Energy Laboratory, recently published "Fuel consumption impacts of auto roof racks" in the journal Energy Policy, using data collected from crowdsourcing and online forums. Their research showed that while aerodynamic drag was more negatively affected when roof racks were loaded, efficiency losses observed during miles logged with unloaded racks were far more significant. In short, because people drive around a ton with their roof racks empty (eight times more than when loaded), it would be smart to remove them to save gas and money.
The study acknowledged that current roof rack designs could be more aerodynamic, or perhaps easier to remove to encourage people to remove them when they're not in use.
Meier and Chen determined that roof rack usage, due to growing national travel trends, will go up by about 200 percent by 2040. At that rate, all of the losses we're seeing as a country from inefficiencies cause by roof racks will outweigh the total footprint of the gains from alternative-fuel vehicles.
"For comparison, the additional fuel consumption caused by roof racks is about six times larger than anticipated fuel savings from fuel cell vehicles and 40 percent of anticipated fuel savings from battery electric vehicles in 2040," the study reads.
In our own day-to-day usage, we noticed significantly worse fuel economy and increased wind noise with a Mopar rack mounted on our departed Four Seasons Jeep Cherokee. It was also a nightmare to remove, so we never even tried to fix the issue. If it had been easier, or better designed, we could have saved quite a bit of cash, it seems.