The Toyota Prius Prime earns the Automotive Science Group's Best All-Around Performance crown. Tesla, BMW, Chrysler, Ford, Hyundai and Kia plug-ins also honored.

The Automotive Science Group (ASG) conducted their yearly study assessing efficiency and cost to determine this year's best vehicles. In calculating CO2 emissions, ASG takes into consideration raw material extraction, the manufacturing process, fuel efficiency, and the vehicle's end-of-life. This year the Toyota Prius Prime took home the Best All-Around Performance Car and Best Environmental Performance Car of 2018.

Launched internationally in 2000, the original Toyota Prius boasted 41 MPG. Impressive for its time, the Prius held 295 grams CO2-e emissions per mile driven over its lifetime.  Today, the most efficient non-plug-in Prius is the Prius Two Eco. That model increases efficiency to 56 MPG and 226 grams CO2-e emissions per mile.

While this is an impressive improvement, it pales in comparison to the plug-in hybrid Prius Prime. The Prime features 133 MPG-e and 25-miles of electric range. Based on the CO2 lifetime emission study conducted by ASG, the Prime holds a mere 181 grams CO2-e emissions per mile driven over it's life. This accounts for a 39% improvement over the original Prius. For comparison, the smallest carbon footprint for a non-electrified powertrain was the Mitsubishi Mirage at 301 grams CO2-e per mile.

While many EV enthusiasts would likely value electric range above all else, the Prime won out over some tough plug-in competition for the top efficiency award. It also bested other traditional hybrid and small cars such as the Mitsubishi Mirage, Chevrolet Spark, Toyota Yaris, and Toyota Prius Eco.

However, while the Prime took top honors for 2018, it was far from the only plug-in represented. The Tesla Model XBMW i3, Ford Focus ElectricHyundai IONIQ PHEV, Kia Niro PHEV, and Chrysler Pacifica Hybrid all won Best Environmental Performance in their respective vehicle categories.

The Chevrolet Bolt, Nissan Leaf, and Mitsubishi Outlander PHEV all earned Best 5 distinctions. Tesla was also awarded the Best Environmental Performance Brand of 2018.

Gallery: Toyota Prius Prime Tops Automotive Performance Index Study

Source: Automotive Science Group