New vehicles rolling off car lots this summer are more efficient than ever, tying highs in rated fuel efficiency set earlier this spring.

Researchers at the University of Michigan's transportation research institute just released new data on the fuel economy of new cars and trucks sold in July. It shows a slight increase since June and a strong 4.7 miles-per-gallon improvement since the fall of 2007.

Advertised fuel mileage has increased by 1.2 miles per gallon this year over 2012 models:

These figures come from combining monthly sales of cars, SUVs and pickup trucks with EPA fuel economy ratings. One important caveat: they are for fuel ratings, not actual fuel consumption. (The government is currently reevaluating its sticker rating system after concerns that automakers overstate fuel economy.)

Although fuel economy advertising can be imprecise, the energy and environmental performance of vehicles is also increasing. When looking at actual fuel consumed since the fall of 2007, we can see a steady drop that correlates with the improvement in sticker ratings:

Recent laws are helping to push these improvements. In 2007, George W. Bush signed a law increasing fuel economy standards for light vehicles to 35 miles per gallon by 2020. And last year, the Obama administration worked with automakers to increase those standards to 54.5 miles per gallon by 2025.