With rising gas prices and increasing environmental concerns, improving fuel economy has become a top priority for many car buyers. A mileage rating of 50 miles per gallon (MPG) represents a milestone in fuel efficiency that could significantly reduce fuel costs and emissions. But is reaching the coveted 50 MPG benchmark really achievable with today’s engines and technologies?
The Quest for 50 MPG
The 50 MPG target is not plucked out of thin air – it actually has origins in U.S. fuel economy regulations. Up until the mid-1970s, cars and trucks in America were not subject to any fuel economy standards at all. But in 1975, Congress passed the Energy Policy and Conservation Act, which established the first standards for passenger vehicles sold in the U.S. These standards called for a fleetwide average of 27.5 MPG by 1985.
The fuel economy bar was raised further in 2007, when Congress passed new regulations that set a 35 MPG fleetwide average to be met by 2020. And in 2012, standards were again increased to mandate a fleet average of 54.5 MPG by 2025. The upcoming 2025 standards equate roughly to a real-world rating of about 40 MPG combined for an individual vehicle. Getting to 50 MPG for a single car would exceed this level by a significant margin.
Car manufacturers have invested heavily in innovations to continue improving mileage with each new model release. Turbocharging, direct injection, start-stop systems, and advanced transmissions have all helped boost efficiency. Electric cars like the Tesla Model 3 have also started to enter the mix, providing effortless torque and zero tailpipe emissions. Yet even with all these advancements, most mainstream gasoline-powered cars still fall short of that elusive 50 MPG mark.
Why 50 MPG is So Challenging
Reaching 50 MPG represents an engineering challenge due to the innate compromises involved in powering a large metal box down the road at high speeds. Let’s take a look at some of the key factors:
Pushing a 3,000 lb vehicle through the air at 65 mph requires overcoming tremendous aerodynamic resistance, also known as drag. Reducing this drag is essential for achieving maximum mileage. An aerodynamic shape with a low front end, tapered rear, and minimal exterior appendages helps minimize turbulence. But even the sleekest designs still face substantial aero drag forces at highway speeds.
In addition to air resistance, the friction between tires and road surface causes “rolling resistance” which also saps energy and fuel. Low rolling resistance tires help cut this friction, but the grip and durability demands of tires limit just how low this resistance can go while maintaining safe handling.
The engine, transmission, driveline, and other powertrain components have inherent energy losses and inefficiencies that show up as wasted fuel. Engineers continue finding ways to reduce friction, allow operation at lower rpm, and optimize airflow and combustion. But no car engine can convert 100% of the fuel energy into motion.
The heavier the vehicle, the more force it takes to accelerate and climb hills. Vehicle mass directly contributes to inertia, rolling resistance, and powertrain losses. Designers use lightweight materials and component optimization to pare weight where possible, but safety regulations, customer demands, and the physical reality of transporting passengers and cargo safely put a lower limit on just how light an everyday vehicle’s curb weight can realistically be.
The factors above represent physical challenges that constrain how efficiently a gas-powered vehicle can use fuel energy. How close can automakers get to 50 MPG given these immutable barriers?
The Most Efficient Gasoline Vehicles
Looking across today’s car market, a small number of models using ingenious engineering solutions do manage to surpass that 50 MPG threshold.
2022 Hyundai Ioniq Blue
The top gasoline fuel sipper for 2022 is the Hyundai Ioniq Blue hatchback. By combining a sleek shape with an ultra-efficient powertrain, the Ioniq Blue is rated for an EPA estimated 58 MPG combined. Key enablers include:
- Slippery shape with a 0.24 drag coefficient
- Low curb weight of just 2,711 pounds
- Advanced 1.6L 4-cylinder engine with direct injection
- 6-speed dual-clutch automated manual transmission
- Low rolling resistance tires inflated with high pressure
This suite of efficiency measures allows the Ioniq Blue to reach lofty mpg heights under ideal conditions. However, some reviewers have found its real-world mileage does fall short of the EPA rating.
2021 Toyota Corolla sedan LE Eco
Another compact economy car reaching the 50 MPG mark is the 2021 Toyota Corolla LE Eco. Its EPA rating comes in at 53 MPG combined, enabled by features like:
- Low 0.27 drag coefficient
- Light 2,865 lb curb weight
- 1.8L 4-cylinder engine with variable valve timing
- Continuously variable transmission
- Low rolling resistance tires
The Corolla shows that with obsessive attention to efficiency, a conventional powertrain in a basic small car can achieve 50+ MPG in ideal conditions.
The Challenge of Real-World MPG
While the EPA test cycle is useful for comparison, fuel economy in actual driving rarely lives up to the official rating. Aggressive driving behavior and use of accessories like air conditioning can reduce real-world mileage by 15% or more. Frequent short trips and cold weather also often result in lower than advertised efficiency.
When examined outside laboratory conditions, many 50+ MPG vehicles end up in the mid 40s for combined city/highway driving. That’s still thrifty for a gas engine, but highlights the on-road challenges of reaching the heights suggested by MPG window stickers.
Plug-in Hybrids Bridge the Gap
Plug-in hybrid cars like the Toyota Prius Prime and Honda Clarity can operate in pure electric mode for shorter trips, resulting in extremely high mileage figures when gas usage is minimal. Their official MPG ratings are:
- Toyota Prius Prime: 133 MPG equivalent combined
- Honda Clarity Plug-In Hybrid: 110 MPG equivalent combined
These numbers are based on electric-only range at zero gas consumption, charged by grid electricity. Once the battery is depleted, gas mileage falls back down into the 40s. Still, PHEVs show the potential of electrification for radically cutting fuel use for around-town driving.
The All-Electric Path to 50+ MPGe
Pure battery electric vehicles (BEVs) have no tailpipe emissions and can convert over 70% of electrical energy into motion – far exceeding the maximum theoretical efficiency of a gas engine. With access to cheap overnight charging, today’s long-range EVs can achieve energy efficiency equivalent to 100+ MPG in real-world use.
The “MPGe” metric converts electricity consumption into an miles-per-gallon equivalent figure to facilitate comparison with gasoline vehicles. Let’s look at MPGe ratings for today’s most efficient EVs:
|EV Model||MPGe City / Highway / Combined|
|Tesla Model 3 RWD||142 / 121 / 132|
|Polestar 2||116 / 103 / 110|
|Nissan Leaf||123 / 99 / 111|
|Kia Niro EV||123 / 102 / 112|
As the table shows, all-electric range of 200+ miles is now commonplace, and efficiency scores well over 100 MPGe combined can be achieved. And unlike mpg stickers, these figures tend to be quite accurate to real-world use with minimal degradation from driver behavior or climate conditions.
For those needing to drive long daily distances, EVs may still fall short due to charging requirements. But for suburban commuting and errands within 100 miles roundtrip, today’s EVs deliver efficiency on par with 60 to 70 mpg in a compact hybrid or diesel – without any tailpipe emissions.
The Path Ahead
Further gains in fuel efficiency beyond today’s most miserly gas vehicles will require significant powertrain breakthroughs. Small enhancements may yield another few MPG, but engineering physics indicates that wringing more than about 60 MPG from a pure gasoline car will remain a major challenge. Diesels can see slightly higher ratings, but face emissions challenges.
Meeting upcoming CAFE requirements will likely require wider adoption of 48-volt mild hybrid systems, allowing engine stop-start and modest electric assist. Further electrification through full hybrids and plug-in hybrids can offset gas usage during around-town trips. And all-electric models make the most sense for commuters with reasonable access to daily charging. For heavy highway travel, class-leading diesel or hybrid models in the 40-50 MPG range remain the top options.
While a 50 MPG gas car may not quite be feasible as an across-the-board solution, continuing refinement of efficiency technologies combined with thoughtful electrification can help more drivers get closer to that elusive 50 MPG dream.
Reaching 50 MPG in a gas-only vehicle requires overcoming tremendous inherent barriers from physics. A tiny number of ultra-efficient compact cars like the Hyundai Ioniq Blue can achieve EPA ratings over 50 MPG combined. However, their real-world economy is likely to fall short of window sticker numbers.
For most drivers, the path forward for maximizing fuel efficiency relies on hybridization and increased electrification. Mild hybrids, full hybrids, plug-in hybrids, and EVs can all achieve 50+ MPGe in favorable driving conditions. Combining the right vehicle technology with wise purchasing decisions and eco-driving techniques will get more people closer to that 50 MPG target.