Quote:
Originally Posted by Z man
The Prius is very similar to the Yaris, Corolla, or xA at highway speeds (same 1.5L), and those cars get great MPG.
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Those cars do get great highway mileage, and anyone trading up from a 18 mpg car is doing a good thing. But the Prius is better. The Prius gets better mileage on the highway because it uses an Atkinson cycle engine rather than an Otto cycle engine. The reason the Prius can use an Atkinson cycle engine is that the electric motors are, contrary to myth, able to be used at any speed to boost horsepower. If you are cruising along at 65 MPH, and punch it, the Prius engages the electric motor as well as feeds the ICE more fuel. Without the electric motor assist, it would be a lesson in lethargy.
There's a good article about the difference between the Prius and Toyota Echo engine which appear to be exactly the same (except for the Atkinson vs. Otto cycle) at
http://www.cleangreencar.co.nz/page/prius-petrol-engine.