Fuel Economy Went Nowhere for Five Years, Then Jumped 30%

Cars get more efficient every year — that's the assumption. I averaged the best-rated fuel economy figure for every model in our catalogue and grouped by era. The line is not smooth.

The early 2000s went backwards

26.5 mpg against 27.5 in the late 1990s. Cars got thirstier for half a decade.

Cheap fuel and a market moving hard into SUVs and trucks. Efficiency was available as engineering but nobody was buying it, so nobody sold it. This is the clearest evidence you'll find that fuel economy tracks fuel prices and regulation rather than technical capability.

The flat decade

Then the strangest part: 37.8 mpg in the early 2010s and 37.8 in the mid 2010s. Identical. Five years of development producing no measurable improvement in the headline number.

Development didn't stop — it went into weight, power and equipment instead. Cars grew four inches wider over roughly this period, as we found in cars grew four inches taller and wider, and gained sensors, screens, sound insulation and safety structure. Engines got substantially more efficient, and the gains were spent carrying the extra mass rather than showing up at the pump.

Then the jump

49.4 mpg in the 2020s, up 31%. This one is a mix shift more than an engine breakthrough — hybrids moved from niche to mainstream, and plug-in and full-electric models entered the ratings with figures no combustion car can approach.

The average is being pulled up by a new category rather than by conventional engines suddenly improving. A 2022 petrol sedan is better than a 2015 one, but not by 31%.

What this means when buying used

The mid-2010s are the value sweet spot for a petrol car. A 2015 model gives you essentially the same economy as a 2019 one at a much lower price. If the badge doesn't matter to you, the efficiency argument for buying newer largely disappears across that stretch.

Avoid the early 2000s if running cost matters. That era is genuinely worse than what came before it, and cheap purchase prices there get eaten at the pump.

The 2020s gain is mostly electrification. If you want the 49.4 figure you're buying a hybrid or an EV, with the battery-health questions that come with a used one — which is why the state-by-state supply picture matters, as we covered in Hawaii's lots are 6.3% electric.

Verify the specific car's configuration. Economy varies enormously by engine and drivetrain within one model line, and the figure quoted in a listing is often the best trim rather than the one on offer. A VIN check decodes the actual engine and drivetrain that car left the factory with.