If we asked you to name a car that featured class-leading horsepower with 40-mpg highway fuel economy, the detail-obsessed among you would quickly say the 2012 Hyundai Accent or the 2012 Kia Rio.

If we took that one step further and asked you to name a car that costs less than $15,500, gets 40 mpg highway and comes with a segment first Idle Stop and Go system, that would probably stump the majority of readers.

The answer is the 2012 Kia Rio, which will become the first non-hybrid and non-luxury car to incorporate a fuel-saving stop and start system, although this feature won’t hit the market until some time in 2012.

It’s likely that only automatic transmission models will be so equipped, which is why the price of entry jumps from from $14,150 to “under $15,500.” The lowest priced Kia Rio sedan starts at $14,150 with a six-speed manual transmission, but that price does include a $750 destination charge.

The 2012 Kia Rio sedan with a six-speed automatic transmission will start at $15,250 including destination charge. All models get a Hyundai-sourced 1.6-liter four-cylinder engine, which gets an EPA rating of 30 mpg city and 40 mpg highway while delivering a best-in-class 138 horsepower.

Unlike earlier Rio models, which made features like air conditioning and electronic stability control optional, the 2012 Kia Rio sedan comes well equipped. All trim levels get A/C and a range of safety features that includes anti-lock brakes, stability control and vehicle stability management.

Kia builds the Rio with an eye on the environment as well: 85 percent of the materials used in the Rio’s construction are recyclable at end of life, and the Rio’s seat foam is made from renewable, plant-based castor oil instead of petroleum.

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