It’s a fact of life, Ted, that fuel-efficiency has been a big focus for car-makers in the last decade. So, the most economical models tend to be the newer ones which tap into better technology (such as stop-start functions) and improved engine and driveline designs.
But beyond the improvements in petrol-engine technology, diesel engines have brought some big improvements, as have hybrid vehicles. The real headline makers have been, of course, the plug-in electric vehicles which are now available second-hand for sensible money. I’ve seen Nissan Leafs for sale for less than $20,000 and the plug-in hybrid Mitsubishi Outlander PHEV for similar money.
If economy is your number-one aim, stay away from all-wheel-drive cars as the extra driveline friction requires more power and, therefore, fuel to drive it. And don’t forget that how you drive, where you drive and even whether you check you tyre pressure regularly can also have a huge effect on your ultimate fuel economy.