The Prius's true advantage on the highway stems from it's use of the Atkinson cycle engine. The ICE has low torque and less HP than the similar ICE in the Echo BUT, it is more fuel efficient and produces fewer emissions.
When cruising at hwy speed you need neither high torque nor significant horsepower. Thus, at cruise speeds a non-Atkinson vehicle is actually at a disadvantage b/c its inefficient stroke ratio produces more power than necessary in it's most efficient rpm range...thus, it runs in a lower rpm range where it's fuel efficiency is not as good.
Since the Prius need not use 'gears' it can run continually in it's most efficient rpm range, plus has the more efficient stroke ratio and thus performs better.
Now, before you ask, what about when you need the torque and HP like when passing or accelerating from a stop? Enter the electric motor...it has a tremendous amount of instantaneous torque for it's size and it runs off of the excess energy produced and then stored in the battery thanks to the Power Split Device keeping the ICE in it's most efficient range and spilling the excess to the battery.
Now, I'm sure someone else mentioned it, but if you've ever set an Echo and a Prius side by side you'd understand in a heart beat why someone would prefer the Prius. It's half-again or more more spacious, more comfortable, has more features, more cargo room, and a hell of a lot more fun.
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The Prius's true advantage on the highway stems from it's use of the Atkinson cycle engine. The ICE has low torque and less HP than the similar ICE in the Echo BUT, it is more fuel efficient and produces fewer emissions.
When cruising at hwy speed you need neither high torque nor significant horsepower. Thus, at cruise speeds a non-Atkinson vehicle is actually at a disadvantage b/c its inefficient stroke ratio produces more power than necessary in it's most efficient rpm range...thus, it runs in a lower rpm range where it's fuel efficiency is not as good.
Since the Prius need not use 'gears' it can run continually in it's most efficient rpm range, plus has the more efficient stroke ratio and thus performs better.
Now, before you ask, what about when you need the torque and HP like when passing or accelerating from a stop? Enter the electric motor...it has a tremendous amount of instantaneous torque for it's size and it runs off of the excess energy produced and then stored in the battery thanks to the Power Split Device keeping the ICE in it's most efficient range and spilling the excess to the battery.
Now, I'm sure someone else mentioned it, but if you've ever set an Echo and a Prius side by side you'd understand in a heart beat why someone would prefer the Prius. It's half-again or more more spacious, more comfortable, has more features, more cargo room, and a hell of a lot more fun.