Surprising MPG crossing Appalachians

wow, incredible! what was your average speed?

 

those are great info displays, thank you.

 

I've noticed that since the weather has warmed up I've been getting closer to 70 calculated at the pump, good stuff!

 

How fast were you driving on the interstate? So it does seem the lithium ion does bump up the fuel economy all the way around.

 

Here’s from driving around a little bit yesterday around Boise in side streets mainly.



iPhone ?

 

I recently did a mountain trip as well over a 7000ft mountain pass. From end to end including some freeway I got 60 MPG for the trip (according to the computer). The latest Prius is just stunningly efficient.

In line with your numbers, I think the main thing is speed. The mountain road I took was limited to 45-55 MPH because it was windy so on my way down I didn't need to use gas to keep up with traffic when the road leveled out. If the speed limit was higher, I would have had to burn gas and then waste energy using the friction brakes on slopes.

 

I bet the 'B' transmission setting for engine braking would have negated the need for friction brakes and would boost your economy up over 100 mpg. You would do that once the battery was fully charged from regenerative braking.

I'm pretty surprised to hear of such high economy going over the mountains. What I've seen is that it spikes up quite high going down the side, but then dips down equally low when climbing. Haven't tried it in my Prius yet though!

 

B mode should only cool and save the friction brakes, not provide any boost to MPG.

My experience is that high average elevation improves MPG, thanks to both reduced drag in the thinner air, and (mostly in non-hybrids, not so much in the Atkinsonized Prius) reduced engine 'pumping' loss. The primary problem with mountains is steep descents requiring friction or engine braking, wasting gravitational energy that could have provided nice glides on shallow slopes. With shallow descent angles, the car can often glide well and entirely recoup the extra energy required for the initial climb, and end up with excellent overall trip MPG.

 

It is a boost in economy because the engine is using hardly any fuel; inertia keeps it spinning. At least that's how it works in conventional engines, as evidenced by the instantaneous fuel economy read-out. I believe the 'B' mode in Prius mimics that, in order to get engine braking.

 

On these downhills, the Prius engine uses zero fuel, in both D and B modes, so B isn't an improvement on this score. This clearly shows on a ScanGauge-II (or other OBDII-ort engine monitor) fuel consumption display, which isn't capped to the 100 or 200 MPG display limit (depending on model year) of U.S.-market Prii.

Modern conventional engines should also be burning no fuel on these downhills, whether downshifted or not, also as shown on the same ScanGauge display. I believe it is labeled DFCO, deceleration fuel cutoff, and I see it in both my present and past Subarus.

On shallower hills, one may find conditions where high gear burns some fuel but downshifted does not. But on steeper hills, it should be zero in all practical gears.