Question on PRIUS Highway MPG

Nice! Excellent explanation there, thank you .
From what I have read, it seems like prius can actually do alot better on the highway than on the city since the engine is only asked to run at low/idling rpm. I'm not sure if the heretic mode is the culprit that brings the highway mpg down according to EPA estimates. Or maybe because on highway, the vehicle doesn't do much regenerative braking.

 

On the highway there is no or very little use of regenerative braking.
On the highway there is little ICE shutoff (either just fuel or complete shutoff) as most major highways are relatively level and/or when you do find a nice downhill section the aerodynamic load at the speeds most people travel is about equal to the coast power released by gravity. Unless you are in the mountains.
Most cars get their best mileage between 40-50 MPH or 65-85 km/hr. This includes Prius. Most major highways are posted way above that, and most people travel above that posting. Including most Prius drivers.
So the result is slightly poorer mileage on the highway than in the city.

I will also state that the "new corrected" (as from 2006 I think) EPA rating for the Prius is actually fairly accurate, if you drive "normally". You can get worse and you can get better. If you just drive you will get close to the rating. Note that the Canadian rating is similar to the old EPA one and is very "optimistic". I don't know of anyone who consistently gets 4.1 l/100 km in the GII and below 4 l/100 km in the GIII.

Do note that the "motor" (electric portion) IS used effectively on the highway to make up for small drops in speed. This saves fuel that would be needed for acceleration enrichment in a "normal" car. If you watch the MFD you can see this in action.

Note further that the ICE always spins if you are traveling above 42 MPH. If the car goes to "coast" there is no fuel injected, but the ICE is spun by the electric motor. This is to protect MG1 from overspin.

 

The 51 mpg part (mine says 48 highway) is not inflated at all. I bought mine last week. It only has 301 total miles on it (had 47 when I bought it) and I got almost exactly 51 mpg in city only driving. The only reason I topped it off is I am taking a 500+ mile highway trip tomorrow and want to get an accurate comparison. This is with an "un-broken-in" engine. My mileage should increase by (supposedly) 10-15% after a 5-10k breakin period. So far, I'm a happy camper!!

 

You have raised from the dead a thread about the Gen 2 Prius that ended 4 years ago. You have a Gen3 Prius, so there will be noticeable differences if you try to use Gen 2 facts as Gen 3 facts.

 

Wow. Didn't even notice. I guess I'm just REALLY excited right now!!!

 

You have a new Prius, you have a right to be excited!

 

Stratman,

Enjoy that new Prius. You have that right! And "Welcome" to Prius Chat.