Why did we look at EPA combined figures instead of highway or city numbers? Based on our independent testing, the EPA's combined figures, which are a weighted balance based on 60 percent city driving and 40 percent highway driving, are far more realistic for the way most people drive. And the EPA seems to agree since the new federally-mandated window stickers that are currently being phased in highlight the combined figure rather than individual highway and city numbers.
If saving fuel at any cost or complexity is your goal, you'll probably be more interested in our recent roundup of the industry's most efficient vehicles that don't need to be plugged in. But hybrids, plug-in hybrids and extended-range EVs aren't for everyone since their initial purchase prices can take years to recoup.
Diesel or gas?
A look at the list reveals two camps: Diesel German-branded cars and a mishmash of gas-powered minicars and subcompacts.
Not surprisingly, the top two performers on the list are the only two city-oriented runabouts on the market, the Scion iQ and the Smart fortwo. Both are geared, literally, for urban users, so their EPA city figures are as good as you'll get in from a non-hybrid (35 and 34 mpg, respectively). They suffer at highway speeds, but that's because they were built to prowl city streets.
From there, the real battle begins. Volkswagen's remarkably thrifty midsize sedan makes a surprise appearance in third place. Although just one trim level is available with the slightly more thrifty manual transmission, all Passats are particularly aerodynamic, which helps keep every diesel-powered model on our list.
The Passat's same four-cylinder diesel, which the automaker refers to under the moniker TDI, shows up in more than half of the 34 mpg cars on the list. We'll call it the clear mpg champion among non-electrified cars. Given the wide range and size of vehicles that benefit from this torquey diesel engine, it's clear that low-rpm diesels still rule when it comes to saving fuel. Why? High combustion temperatures aid efficiency and diesel fuel contains a significantly higher level of energy than gasoline.
No other non-premium automaker currently offers a diesel engine in the U.S., although Chevrolet and Mazda are both set to enter the market next year.
Accordingly, the bevy of Kia and Hyundai models also on our list make use of a gas-powered engine: A new-for-2012 1.6-liter four-cylinder. While both the Rio and the Accent share a powertrain and a platform, they go about things a little differently. Hyundai's Accent is a little less stylish but a little more refined, but Kia's Rio is undeniably the looker and it offers a special Eco trim package that includes fuel-saving start/stop functionality. All of the Hyundais and Kias feature a driver-selectable Eco button (pictured above), which remaps throttle response to save about 7 percent more fuel, the automakers say.
Of course, any driver can eke out maximum fuel economy, but having a thrifty package from the package is an essential first step.
The 10 most fuel-efficient non-electrified cars you can buy
1. Scion iQ 37 mpg
2. Smart fortwo 36 mpg
3. Volkswagen Passat TDI (manual) 35 mpg
4. Audi A3 TDI 34 mpg
(tie) Hyundai Accent (manual) 34 mpg
(tie) Kia Rio (manual) 34 mpg
(tie) Kia Rio Eco (automatic) 34 mpg
(tie) Volkswagen Golf TDI 34 mpg
(tie) Volkswagen Jetta TDI 34 mpg (sedan and SportWagen)
(tie) Volkswagen Passat TDI (automatic) 34 mpg