No we did not. You are comparing apples to oranges. 15-20 years ago cars were 500lbs+ lighter because they didn't have all of the safety engineering that is part of modern vehicles. For example:
Curb Weights
1990 Nissan Sentra Base Model: 2156 lbs 29/36MPG
2010 Nissan Sentra Base Model w/ CVT: 2972 lbs 26/34MPG
You put one of those 1990 engines in a modern car and you won't see anything like the MPG that it got in one of those light-weight chassis of 1990.