You also need to factor in that cars are more efficient now, and there are bypasses/ motorways etc (even if there's also more congestion). You'll get a fair bit further on your 273 litres today than you would have in 1960
I cannot remember the source but this was refuted: cars have now taken up the fuel efficiency with increases in weight and size. If you suddenly come across a car from the 1950s, even like a Rover, you will be shocked at how small it is.
The fuel economy improvement can be refuted, but it's merely a matter of playing games; taking the right 'slices' of time and data. If for example, you take light vehicles (cars, vans, etc.) and compare 1987 to 2017, you can get data that says that average fuel economy has declined from about 21 mpg to 20 mpg. This is due to the population of vehicles being increasingly made of SUVs and mid-sized cars. You can also compare a Ford Model T at 25 mpg to any of a number of larger Ford models (or the average mileage) and 'show' that fuel economy is not better today than it was then. But if you compare like-for-like fuel economy has improved considerably. It's just that many people choose to buy the largest car they can afford to run, which means that the population of personal cars have gotten larger, which at least eats into any fuel economy comparisons, and with the right selection of vehicles can eliminate it altogether.
If, on the other hand, you consider something like the VW Polo, which at one time held the record for the best fuel economy in actual long distance driving in the UK (I don't know if it still does), the 72 mpg accomplished to set the record is a huge improvement over the 25 mpg that was the best a Model T could deliver.
And there's the Toyota Eco Spirit, a 100 mpg concept car that was never produced.
“In some ways, it is easier to be a dissident, for then one is without responsibility.”
― Nelson Mandela, Long Walk to Freedom