Small cars don't always deliver the best fuel economy. Here's what does.

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You don't have to cram into a compact car to get good gas mileage. In fact, three popular midsized sedans we've recently tested get the same or better mileage than any non-hybrid, non-diesel small car. Despite attractive sticker prices, econoboxes are often not the best choice.

The most fuel-efficient, five-passenger economy car with an automatic transmission that we've tested is the Toyota Yaris, which gets 32 mpg overall. But we've recently tested three mainstream midsized sedans that do just as well or better: the Honda Accord (30 mpg overall), Nissan Altima (31 mpg overall), and Mazda6 (32 mpg overall).

Small sedans don't do much better. The most frugal models--the Toyota Corolla and Mazda3 Skyactiv--also get 32 mpg overall. The Ford Focus gets 31, but only with its special $495 Special Fuel Economy package. Other small cars get between 26 and 29 mpg.

If you're willing to spend a little more to get even better gas mileage, several comfortable midsized sedans with hybrid and diesel-powertrains are nipping at the heels of our mileage champ Toyota Prius, which boasts 44 mpg overall. The Ford Fusion Hybrid gets 39 mpg Toyota Camry Hybrid returns 38 mpg, the Ford C-Max and Volkswagen Passat TDI diesel delivers 37 mpg. No small sedan or budget hatchback can even approach those numbers.

So what's going on?

Two things: First, aerodynamics. Larger, longer sedans give more room for air to flow smoothly off the back of the car than shorter models. That reduces drag on the highway.

Secondly, automakers can charge more for larger cars, giving them latitude to add the latest fuel-efficiency technology that may not be cost-effective to put on smaller cars, such as hybrid systems and direct fuel injection.

So far, the trend of midsized cars getting the same fuel economy as smaller ones applies only to sedans. Smaller SUVs still tend to get better fuel economy than larger ones.

We're happy to see consumers have a choice of larger sedans that get excellent fuel economy, with prices typically starting in the low to mid $20,000 range. Not only are they more comfortable and versatile, midsized sedans also safer in accidents, all other things being equal.

The real takeaway is to do your research, and not make assumptions based on size or even powertrain. Spending a few minutes checking our ratings may point you to a better car and a better value.

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