Car bike racks definitely have a negative impact on your car’s fuel consumption. Depending on some factors (which we are going to discuss in more detail further in the article), you should expect to get 5-25% worse mileage with a bike rack installed. It happens because of these reasons:
- The main reason is that all bike rack types (trunk-mount racks, roof racks and hitch racks) significantly decrease aerodynamics, which is a key element in the fuel efficiency of any car. Some bike racks (roof racks are the worst from this perspective) cause more mileage decrease than others (trunk racks are the least troublesome). Though at the end of the day all car bike racks do have an impact,
- The second reason is that an installed car bike rack (including, let’s say, 2 bikes on it) will add around 100 lbs to the weight that your car needs to pull. It might seem not that much, but it is 3% more than an average car weight (around 3,000 lbs), which is not that negligible, I have to say.
The key factors that affect the fuel efficiency
To give you a better idea of how much an installed bike rack will cost you in terms of fuel consumption, let’s have a look at the key factors that you need to keep in mind:
- Bike rack type is the most significant factor. There are 3 types: roof racks, hitch racks and trunk racks,
- Car body type plays a big role as well. Box-shaped cars (vans and SUVs) get substantially less affected than other types (sedans and hatchbacks),
- Either the bike rack is empty or not is a big deal for obvious reasons,
- The speed of your car also has a big impact. The higher the speed is the more pronounced the decrease in aerodynamics is going to become.
With that being said, let’s go through each factor in more detail and take a look at certain numbers.
This article is based on the data from the consumer reports test, my own experience and the experience of other people that I have found online.
Car bike rack types and fuel consumption
Roof bike racks and fuel efficiency
Roof bike racks are the biggest troublemakers in terms of fuel efficiency. I believe the reason is quite obvious since a roof rack system with installed bikes pretty much resembles a sail that works against us.
When it comes to certain numbers, you can expect to get 10-25% less mileage. The more the shape of your car resembles a box, the lesser impact will be. The faster you drive, the higher impact you should expect.
For example, for an SUV driving not that fast it will be closer to a 10% reduction in mpg, whereas a fast driving sedan can get even a 25% reduction in mpg.
Hitch/trunk bike racks and fuel efficiency
Even though it might seem not a big deal from the aerodynamics perspective to have a relatively small thing attached to the back of your car, in fact, it disrupts the streamlining of the rear of your car in a big way. As a result, hitch and trunks bike racks are not much better in this regard.
When it comes to certain numbers, you can expect to get 7-20% less mileage. The rules are the same here as for roof racks. Not fast driving shape-box cars get less affected, whereas fast driving sedans and hatchbacks significantly more.
Truth to be said, trunk-mount bike racks are the most fuel-efficient. The reduction in mpg can be just 5-7%, which is bearable.
Car body types and fuel consumption
SUVs/vans with bike racks installed and fuel efficiency
As we have discussed earlier, the shape of your car matters a lot.
SUVs and vans get twice less affected in comparison to sedans and hatchbacks. Why? Because SUVs and vans are not that great in terms of aerodynamics from the very beginning so bike racks have less of an impact.
The average reduction in mpg for SUVs and vans is going to be 13%: closer to 18% for roof racks and 10% for hitch/trunk racks.
Sedans/hatchbacks with bike racks installed and fuel efficiency
Sedans and hatchbacks owners are the ones who are going to pay the highest price.
Having this car type with a bike rack installed and 2 bikes on it, you will get a 15% reduction in mpg on average: closer to 18% for roof racks and 12% for hitch/trunk racks.
Does it matter much if your bike rack is empty or not?
Yes, with actual bikes put on any bike rack type the fuel consumption is going to skyrocket.
For SUVs/vans (at 65 mph):
- Roof racks mpg reduction with 2 bikes is approx. 17%, with an empty roof rack is approx. 3%
- Hitch racks mpg reduction with 2 bikes is approx. 10%, with an empty hitch rack is approx. 2%
For sedans/hatchbacks (at 65 mph):
- Roof racks mpg reduction with 2 bikes is approx. 18%, with an empty roof rack is approx. 6%
- Hitch racks mpg reduction with 2 bikes is approx. 12%, with an empty hitch rack is approx. 3%
Does it matter much how fast you drive?
I have not performed such sort of tests myself. Also, I have not managed to find any consumer reports regarding how exactly the speed affects the fuel consumption of a car with a bike rack mounted.
However, I guess nobody will argue that it is quite obvious that the speed matters a lot. As a result, if you mostly drive through neighborhood areas, you will be blessed to have an insignificant mpg reduction.
Something around 5-7% with two bikes, and basically 0% with an empty rack.
A tip on how to decrease this effect
Hitch bike racks with lower positioning tend to perform better than hitch bike racks with higher positioning. It might be the case because it is more crucial from the fuel efficiency standpoint to have better aerodynamics closer to the top of your car.
So to speak, if you drive with bike racks a lot, then your fuel economy might negate the higher price of high-quality hitch racks.
Conclusion
The fuel consumption with a bike rack installed depends on a bike rack type, car’s body type and speed.
Hitch bike racks are the most fuel-efficient, especially when installed on SUVs and vans. Whereas roof bike racks will cost you more, especially when mounted on sedans or hatchbacks.