Also wrong. A big car doesn't have to be heavy. Especially in comparison with old cars. It's all about how you drive a car not what car.
That "study" is biased as fuck.
"doesn't have to be" but in practice they in fact are. I wouldn't call this a bias problem; it's that people are making and selling and buying huge and inefficient vehicles.
The newer engines are a lot more efficient, but in the US (and a lot of other places) that increased efficiency has been used to move a bigger heavier vehicle, rather than to cut overall fuel use.