I think you may find some of the worst fuel mileage averages were in the early ’70’s. Fuel got very expensve then and our ’60’s muscle cars and our 18′ long, 4,000 lb cars were getting 9 to 12 mpg back then. And a gal. of gas- a whopping 39 CENTS!

In the past 30 years, the EPA has forced the fuel companies to change their fuel to meet pollution standards.

Each time it changes fuel economy goes down.

In 2005 the Hyundai Accent had a 35-37mpg rating
in 2006 it was lowered (as were all cars) to 33-35

It had nothing to do with the cars themselves.

The oil companies raised the ethanol content in the fuel.

The more alcohol you have the worse the fuel mileage is.

which is funny because, it costs less to make and we are paying more for driving less.

So the mileage data you will get from the 80s, will not compare today’s fuels or ratings

I don’t believe it is true, In the 80s cars were smaller but their engines were sucking fuel worse than today’s cars.