May 2017
What’s Driving the Increase in Fuel Economy?
A look into the current MPG ratings has revealed that all vehicle segments are currently at or near the record high for fuel economy ratings. According to the EPA, the overall average fuel economy of vehicles (cars, SUVs, minivans, light trucks & vans) has increased by 5.5% since 2004 model year (MY) vehicles.
When looking at combined MPG, there were twice as many SUVs above the 25 MPG level in MY 2016 than MY 2011. The same trend is occurring in the car segment, with the number of vehicles achieving 30 MPG jumping from 39 in 2011 to more than 70 in 2016. And thanks to hybrid and electric vehicles, the number of models with 40 MPG or greater has more than doubled over this same time period.
While this may not come as a surprise, it’s a good sign that manufacturers are making strides in right direction. But what are some of the main factors resulting in this increase in fuel economy across the board? From what we discovered, the major factor resulting in advancements in fuel efficiencies is the combination of new vehicle technologies and a change in the mindset of how engines should operate.
Automatic Start/Stop
A feature that is becoming more and more prevalent, automatic start/stop technology cuts the spark and fuel when the vehicle stops. Once the brake is released, the engine reignites. Being that this system does not have to be engaged at all times; the effects aren’t typically included in the EPA statistics. Testing of these systems has shown anywhere from a 3%-10% increase in fuel economy. A few nice benefits of this feature is that drivers don’t need to do anything differently in order to save on fuel. And the longer you sit idly, the more you save. So next time you’re angrily sitting in a traffic jam, be soothed by the thought of how much fuel you’re saving!
Turbochargers
While Turbocharging does not directly result in increased fuel efficiency, it does allow for a smaller engine with less displacement to be used, which correlates with greater efficiency. It’s becoming very common to see larger vehicles being powered by smaller turbocharged engines. An example of this can be seen in the Chevrolet Malibu:
2015 Malibu (2.5L) – 29 Combined
2017 Malibu (1.8L) – 46 Combined
Direct-Injection
Although direct-injection is nothing new within the auto industry, it’s somewhat new to mass-produced gas engines (it’s been the standard in diesel engines for a while). From 2009 to 2015, the percentage of new vehicles produced with direct-injection climbed from 5% to 46%. Direct-Injection differs from the standard system in that fuel is injected directly into the air-filled cylinders, whereas standard injection engines mix the air and fuel in the intake manifold.
This system helps to improve fuel economy through its ability to accurately regulate the amount of fuel that is needed at any point in time. They have the ability to detect and respond to minor differences between each cylinder, resulting in less fuel being used to fire each cylinder. Direct-injection improves fuel efficiency and generally results in more power when compared with a standard engine (port-injected) of comparable displacement.
Variable Displacement/Cylinder Deactivation
These innovative systems have made their way from the V8 and V12 super engines to the everyday 6 cylinder engines. Though they go by many different names, they all perform the same task. In layman’s terms, these systems are automatically activated during light load operations (i.e. highway driving) and enable half of the vehicle’s cylinders to be “shut-down.” It accomplishes this by keeping the select cylinders’ intake and exhaust valves closed, creating and air “spring” that causes them to compress and decompress on their own. The computer system then cuts the fuel heading to these cylinders, thus reducing the amount of fuel required to power the vehicle. The overall result is typically a 5%-7% increase in highway and cruising fuel economy.
Lighter Vehicles
The lightening of vehicles has been a hot topic for years now, but still remains a battle for manufactures. It can be difficult to lighten the vehicle while keeping the safety and stability of the vehicle intact. However, this battle will rage on, as it’s an extremely effective way of improving fuel economy. The EPA reports that for every 100 Lbs. removed from a vehicle, the fuel economy improves by 1%-2%.
A major focus of weight reduction is in the body material. A good example of this is the Ford F-150, which since model year 2015 has been built with an aluminum body and bed in lieu of steel. This has resulted in trucks that are up to 700 lbs. lighter and increased MPG ratings from 17/23 to 19/25.
As vehicle technologies continue to enable manufacturers to increase vehicle performance, it will be interesting to see what the next major step towards greater efficiency is. We can only assume that the trend to increase vehicle fuel economy will continue. However, recent changes also bring to light the question of whether focus will remain on improving gas powered engines, or if the focus be turned towards hybrid and electric vehicles, resulting in standard gas-powered vehicles plateauing at their current levels of efficiency.
