Americans are driving more gas-guzzling sport utility vehicles while surprisingly cutting carbon dioxide emissions to a record low, the Trump administration said Thursday.

"Sport utility vehicles reached record-high market share, while also achieving record-low CO2 emissions and record high fuel economy," according to the Environmental Protection Agency's report on model-year 2016 vehicles' fuel economy trends.

Smaller two-wheel drive SUVs made up the largest share of SUVs to roll off the assembly line. The agency released the report to show how automakers are meeting the EPA and Transportation Department's joint fuel efficiency and greenhouse gas rules for cars and light trucks.

Although more smaller SUVs were produced, sales of the larger, truck-sized vehicles dominated, making up 29 percent of all sales. The increase in large SUVs resulted in a record combined 41 percent market share for all SUV types for model year 2016.

"Both car SUVs and truck SUVs achieved record high fuel economy and record low CO2 emissions, with car SUVs reaching 26.2 mpg and truck SUVs reaching 22.2 mpg," EPA said. The smaller SUVs had the largest increase in fuel economy, 1.1 miles per gallon more than the previous model year.

However, a separate report released by the agency said carbon dioxide levels for the 2016 model-year vehicles resulted in a first-ever CO2 deficit under its vehicle emissions program.

Overall performance was 9 grams of CO2 per mile over the limit for model-year 2016 greenhouse gas emissions. "This makes 2016 the first model year in which the industry generated a [greenhouse gas] emissions deficit, after generating credits in each of the first four years of EPA’s program," according to the EPA industry performance report. That means most automakers were over the limit for CO2 emissions. Even hybrid-electric pioneer Toyota didn't meet the mark, the EPA said.

The EPA said the increase in carbon emissions was a result of the ratcheting up of fuel economy performance requirements and required improvements in CO2 reductions. That combined with the loss of greenhouse gas credits for making cars and trucks that run on 85-percent ethanol fuel blends, called flexible fuel vehicles. The credits had been available in the first four years of the program as part of EPA's push to drive demand for alternative fuel vehicles.

However, the Obama administration decided to phase out the flex-fuel credit because it was increasingly difficult to prove whether 85-percent ethanol was being used in the vehicles because it is not widely available. The focus of the EPA program is now on electric vehicles.

The EPA highlighted in the market trends study that all five vehicle types under the EPA program have "steadily increased fuel economy in recent years and are at or near their record high fuel economy levels."

"However, the market shift towards SUVs has offset some of the fleetwide benefits that otherwise would have been achieved due to the increased fuel economy within each vehicle type," it added.

Nevertheless, the EPA shows that the final model-year 2016 "adjusted, real world CO2 emissions rate" compared to the 2015 model year is lower for all new personal vehicles. The adjusted rate is 359 grams per mile, which is a 2 gram per mile decrease from model-year 2015 "and the lowest level ever," it said.

The studies jibe with automaker arguments for why the Trump administration should reopen the Obama EPA's review, which concluded that the industry was ready to move forward from the current 35.5 mile per gallon standard to a much stricter 54.5 mile per gallon goal by 2025. Trump's EPA reopened the Obama administration review and is changing the fuel efficiency and carbon dioxide standards to meet the new market trends.

The rise in sales of SUVs and pickup trucks in the last three years resulted from the relatively low cost of gasoline.

Still, sales of light trucks, which include pickup trucks, heavier SUVs, and minivans, are beginning to level off, while still making up 45 percent of production, according to the EPA.

Still, the number is below the record light-truck sales of 48 percent achieved for model-year 2004 vehicles.

The 45 percent achieved in model-year 2016 marked a drop of 2 percentage points. EPA said it expects sales numbers for model-year 2017 SUVs and light trucks to continue to drop.