It wasnt until I actually bought my Prius last Nov that I realized - Eureka! - what the basic benefit of the HSD system was.


Background: I sell Toyota's and have specialized in the Hybrids since they were introduced here in 2001. I've read a lot here and elsewhere but actually having seat time in them is so much more usefull to understanding the concept.

Disclaimer: I am not an automotive engineer but I do have a math/physics background. I will defer to anyone who is actively involved in the field.

All hybrids are basically ICE vehicles. Most of the time they are just like any other vehicle in it's class. an HH is just the same as an ICE HL most of the time! The benefit of the HSD system is that it allows the ICE to shutdown frequently thereby burning no fuel. The more a driver can create times for the ICE to shutdown the less fuel will be used. It's perfectly obvious.. but

A) in cold weather the ICE has to run more because it has more work to do ( heat the cabin, the engine fluids and the catalytic converter );
B) in accelerating the ICE is running nearly all the time;
C) n short trips, see A), the ICE is running for the entire time;
D) during high-speed driving you run into significantly increased aerodynamic resistance which makes the ICE work harder.

In all four of the situations above you are essentially driving a 3.3L ICE Highlander or in the case of the autos a 1.5L Prius or soon a 2.4L Camry.

Our goal as drivers is to maximize frequency of times and therefore the amount of time that the ICE's can shutdown.

Some situations are beyond our control. If you must go to pick up the children at school and return home right away, this short trip will be on the ICE only.