Toyota's fourth-generation Prius hybrid, expected in around 2015, has a tough act to follow.

Still among the most economical vehicles on the market, the third-generation Prius has taken the internal combustion engine to new levels of efficiency--and the new Prius will have to beat it.

To ensure the next-gen Prius is worthy of the badge, Toyota is aiming to make improvements in tire rolling resistance, aerodynamics, and weight savings.

According to Inside Line, sources at Toyota have revealed the company is in talks with tire manufacturers to work on an ultra-low rolling resistance tire for the next Prius, helping it slip along the road even more easily than the current model.

Weight savings will play a key part too, though the company has apparently scrapped the idea of an aluminum body due to high investment costs. Instead, Toyota is likely to make more efficient use of high-strength steel and reduce the thickness of non-structural areas to save weight. However, aluminum may still be used for the hood--just as it is on the 2012 Toyota Prius V.

Toyota will also improve the aerodynamics, possibly taking a lead from the FT-Bh concept shown at this year's Geneva Motor Show.

The concept had a drag coefficient of only 0.235, the result of dramatic moldings and curves to let air slip cleanly by. A production Prius won't be quite so eye-catching, but we'd not be surprised to see some inspiration from the FT-Bh.

There are no clues just yet as to what will power the next Prius, but expect to see some improvements there too.

With improvements all around, will the 2015 Prius be a 60 mpg car? We'll have to wait and see...


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