U.S. fuel economy hit a record high in 2016 and is expected to repeat that in 2017, according to the U.S> Environmental Protection Agency.

The EPA’s Light-Duty Automotive Technology, Carbon Dioxide Emissions, and Fuel Economy Trends: 1975-2017 and Manufacturer Performance reports look at real-world fuel economy, tech trends, and CO2 emissions for vehicles sold in the U.S. The manufacturer report covers compliance by individual automakers with greenhouse gas emissions standards.

While 2016 set a record, the improvement over 2015 was small. Emissions of CO2 fell by 2 grams per mile, and fuel economy was up just 0.1 miles per gallon. The average overall was 24.7 miles per gallon, with 2016 model year cars scoring 28.5 mpg – 0.3 better than last year – and trucks averaging a 0.1 mpg increase to 21.2 mpg.

Preliminary results for the 2017 model year project that CO2 emissions will drop another 7 grams per mile to 352 and fleet fuel economy will climb again by 0.3 mpg to hit 25.2 mpg.

For reference, in 1975, the first year of the report, CO2 emissions neared 700 grams per mile, and adjusted fuel economy was around 13 miles per gallon.

Adjusted CO2 Emissions for MY 1975-20171    Adjusted Fuel Economy for MY 1975-2017

The car fuel economy record has been set and then broken in most years since 2007. But for pickup trucks, this is the first year that fuel economy levels have matched their previous peak set in 1986. Trucks then weighed about a third less than today, which accounts for much of the fuel economy performance.

From 2012 to 2015, most large automakers earned credits by producing fewer greenhouse gas emissions than allowed. This year, eight automakers exceeded targets. Greenhouse gas targets fell in each of those years, now 263 grams per mile, but actual emissions didn’t fall quickly enough to keep up.

SEE ALSO: Consumers Union Tells EPA to Strengthen, Not Lower Emissions Standards

All major automakers had enough emissions credits for 2016 to keep them in compliance for 2016, and most had substantial credits to carry over into next year. The only two automakers with an emissions credit deficit were Volvo and Jaguar Land Rover. The two have three years to come back into compliance.

The biggest deficit in 2016 was from Fiat Chrysler. The company missed targets by 28 grams per mile. But 2.5 million megagrams in credits purchased from Tesla means thta the company stays in compliance. FCA has purchased 22 million megagrams in credits since 2010.

Tops for fleet fuel economy was Mazda, which hit 29.6 mpg, up 0.4 from 2015. Hyundai was second at 28.8 mpg, but Honda is expected to take the top spot  for the 2017 model year with 29.5 mpg. Mazda is projected to fall slightly to 29.3 mpg.

MY 2015-2017 Manufacturer Adjusted Fuel Economy and Adjusted CO2 Emissions

At the bottom of the fuel economy pile were Fiat Chrysler, Ford and GM. Their fleets averaged 21.5, 22.4, and 22.8 mpg respectively. That low performance is easily attributed to the makeup of their fleets. GM, Ford, and FCA sell massive numbers of full-size trucks and SUVs, which lower the average for the fleet.

But Ford and GM’s car lines averaged 28.1 and 27.5 mpg. For comparison, Mazda’s cars averaged 32.5 mpg. Fiat Chrysler’s car fleet averaged 24.1 mpg.

Technology, not weight savings, is what is driving the economy increases. The EPA reports that gasoline direct injection will be in more than half of all vehicles in 2017. That’s up from under three percent in 2008. Mazda is projected to hit 100-percent GDI use in model year 2017, with several other automakers nearing that mark. Turbochargers are now up to 25-percent of the market, and more efficient transmissions are taking over. 25 percent will use seven or more speeds in their automatic gearboxes in 2017, and continuously variable transmissions make up another 24 percent of the market