Ok, here is second full segment in full HV and I am pretty happy with the result.
I would remind people that this is my third hybrid (Gen 1 Insight, Gen 3 Prius, and now Clarity) and I have been hypermileing for many years now.
The car had a full tank of gas, and battery was topped off and EV range was reported as 51 miles. Temp was about 84 average for the trip.
HV mode was engaged in the driveway before moving the car, so the entire trip out and back was made in HV mode. (I stopped for a half hour on the trip, but the car was once again put into HV mode as soon as I turned the car on, so 100% of the
The trip was mostly limited access highway with about 4 to 5 miles on regular roads, but mostly highway access type roads and I probably passed though 12 intersections with traffic lights but by careful hypermile technique, I avoided having to actually stop that much.
The biggest tip for getting a lot of mileage is to watch speed. The posted limit for much of the trip was 65, by my actual speed on the highway probably averaged 62 mph and while some of this was just the speed of the traffic, most of it was just my own desire to go a little slower when I feel that traffic conditions allow it (Hypermilers will usually do the posted limit in heavier traffic to avoid making people angry, but will often slow down a little bit when they can... That is what the sport is about).
Round trip was 35.5 mile. Mileage consumption according the car readout was 71.4mpg. Now this is really excellent. I struggled to get that kind of MPG out of my Honda Insight (mileage plummeted when the AC would come on, and while I am willing to slow down a little bit, I am unwilling to ride around without the AC on). EV Range remaining at the end of the trip was 51 miles.
This is the way the car behaved (for those interested). For the first part of the trip, the car off of the traction motor alone and the ICE did not come on until I entered the freeway on ramp about a mile from my home. As I accelerated on to the ramp the ICE came on and I could see that the mileage readout dropped from 199mpg to about 178mpg just in the time it took to come up to speed. Once at speed, the instantaneous readout showed 42 mpg, and the car display showed that the clutch that couples the ICE to the drive wheels was engaged. The car ran this way for a couple of miles, then the instantaneous readout immediately pegged back up to 199mpg, but the average of course started to lower.
As I cruised, I watched the power readout and I could see that when the ICE was on and the clutch was engaged, the instant display would drop to about 40 to 42 mpg. After a couple of miles, the instant display would jump to 199 and the clutch would disengage so the car was running only on ICE. I had thought that the ICE would mostly stay in direct drive, but it in fact cycles on and off at regular intervals, but when it comes on, it will almost always both show the clutch engaged and the generator also delivering some charge to the battery.
By the time I reached my destination, the mileage consumption had dropped to about 81mpg.
On the return, as soon as I hit the on ramp, the consumption readout fell to about 70 mpg. On the rest of the trip back, it would drop a tiny bit, then the ICE would come on and both drive and charge the wheels, though on slight hills, you could see that the current would reverse out of the battery to supplement the power of the ICE. On the way back, the instant readout would cycle between about 40/42 and 199mpg, and the consumption indicator hovered at 70 to 72 mpg. I suspect that on a very long trip, the mileage consumption would slowly creep down.
On the surface streets, anything over about one and a half major hashes on the power indicator would start the ICE. Very gentle acceleration would allow me to get to 40 or 50 mph before the ICE would kick in, and while I have read that the clutch engages at 47, I found that it does not engage until almost 60 in light acceleration with the ICE running at mid speed (you can hear it but not annoying) to provide extra current. At very low speeds, the ICE is audible when it comes on, but no more so than my Gen 3 Prius was when accelerating at low speed. Of course it is not super placid quite of full EV mode, but it was subdued enough that it was not at all bothersome.
I had expected that at highway speed, the ICE clutch would always stay on, but the car did alternate back and forth between ICE direct drive, ICE Motor generator, and full electric. Perhaps if the car had a couple of passengers and baggage, the ICE clutch would stay engaged more more of the time because gasoline engines are more efficient when the engine is under load at mid range throttle (less pumping loss) but clearly the 1.5L engine is not able to keep the car going up even slight inclines without electric assistance (or at least this is perhaps the more efficient way to do it, which is to keep the ICE running in its most efficient throttle plate opening for the load and using the traction motor to supply the delta power needed for slight acceleration or climbing).
I would assume that the engine does revolution matching when it engages the clutch (good because clutch wear would be a serious concern if it did not) because engagement is so seamless at highway speed that the only thing that gives it away is the very sharp drop in the instant readout.
At the completion of the trip, the EV battery still showed full charge and I used so little fuel that the fuel gauge still read full. Of course this means that I used a half gallon of gas on this trip, but that makes it so that this trip was actually cheaper for me running in HV mode than it would have been in full electric.
This is only my second segment where I ran fully in HV mode, but the first one (about 23 miles) I pulled in 68mpg, and that was mostly around town with almost no highway driving. This was hard to get, but no harder than it was to get that same mileage in the city driving the Prius.
For others that have hypermile experience, I would expect you to be able to get the same result without too much effort. It is a pretty easy car to exceed EPA rating in (the Prius was harder for short trips because of the need to heat the cats, which meant many shorter in town trips I would never get over about 38mpg).
