Prius Eco 58 MPG vs Prius 54 MPG - What's the difference?

it's about an 8% increase, is it not?

 

Correct.

 

Jeff Cobb on hybridcars.com says there's a new more challenging EPA testing cycle for hybrids in 2016, generally lowering miles per gallon. That is to say if using the pre-2016 EPA test protocol, the generation 4 Prius would get higher mpg numbers when released.

 

yeah, i noticed the mpg numbers didn't make sense. but, the eco model has 15" wheels while the non-eco models are mix of 15" and 17", but mostly 17". maybe the non-eco mpg numbers are averaged between 15" and 17" wheel models?

 

@Jeff N Can you elaborate on this statement from your colleague?

 

I'm only a very occassional contributor at HybridCars.com. Jeff Cobb is the editor and primary reporter.

I don't know the details surrounding this issue. I googled around very briefly earlier today and found an article on the investment site, fool.com which doesn't link to an original source but which sounds plausibly based on something real:

Will the EPA's New Fuel Economy Guidelines Crush Automakers in 2016? -- The Motley Fool

I looked around briefly on the EPA's vehicle testing regulation pages but didn't see anything obviously relevant so I don't yet know exactly what the changes are or how they might related to the estimate reporting for the 2016 Prius.

I found the new testing guidelines:

http://iaspub.epa.gov/otaqpub/display_file.jsp?docid=34102&flag=1

This looks geared towards achieving more uniform testing practices between the various car makers and the EPA itself.

Here's another article about it:
EPA unveils new guidelines on automaker mpg label tests

 

Just played with the ecomodder calculator. Neat little tool. 3075 to 3010 lbs and 0.24 cd to 0.22 cd yielded 3-4 mpg difference between 5-60 mph. I'm skeptical of the calculator. Fun to play with.

 

I wonder if the Eco model is programmed to always start in Eco mode and that triggers an EPA test in Eco mode rather than Normal mode.
Perhaps that would get you there along with slight weight reduction, slight improvement in drag coefficient and having both the 15" wheels and more efficient charge discharge cycles from the Lithium battery.

 

Jeff N's first link states:

...this will land for model-year 2017 vehicles, or those that go on sale in 2016.
​

This begs two more questions:
1) If the Gen 4 Prius were to be released just one month earlier than it's anticipated January 2016 availability, would it have earned higher EPA mpg's?
2) For new generation vehicles released this year in 2015, might they have to scale back their EPA ratings next year even if nothing changed? Or is there a grandfather clause? I did not see one. Recertification each year?

 

I don't know, but I did notice that the 2016 VW Jetta gasoline hybrid has a combined EPA estimate of 44 mpg but the 2015 estimate was 45 mpg and this change was there before the recent regulatory cheating scandals became public, I think.

 

I don't think doing the testing in ECO would make significant difference.

 

If compared to the Gen 3, the Gen 4 Normal mode is optimized more for driving feel and the North American Eco mode is optimized more for EPA test efficiency, I suspect the difference between the two modes might be enough in conjunction with the other changes to explain the published mpg numbers

 

The EPA requires a road load to be determined for each car that incorporates the weight, aero, and OEM tire into a value to use as the resistance for the dynamometer. The lighter weight of the ECO will be a factor, but not as much as the artificial weight class in Japan, and it will be more reflective of the real world.

The speed for the road load test was 50mph, but one of Jeff H's posted articles says it is changing to a range of speeds up to 70mph.

Toyota hybrids have in the past, and Wayne Gerdes steady speed tests hints that the gen4 should do so for most trips off of a high speed interstate.

We are used to thinking of hybrids as different from the traditional ICE car, but at the end of the day, they both use only gasoline for all their energy. In the future, when the ICE starts making more use of start/stop and regenerative braking, lines between the two will further blur.

It would seem HSD was pretty much optimized for efficiency with the gen3, and the goal is to further reduce its cost. As to the ECO difference, Li-ion can receive a higher charge than NiMH, making regen more efficient. The non-ECO results could be based on the NiMH model.

This depends on what exactly ECO mode does to the programming. The big change is in accelerator response. The average driver will end up using less throttle for their drive with that change. For these tests, though, the engine has to hit a precise acceleration rate and engine load. All ECO mode does there is cause the tester to simply push the gas pedal in farther for no change in the test results.

 

Speaking of Wayne Gerde: his test drive yielded calculated mpg that was slightly higher than what the car displayed. This is big, lol.

 

There are the mysterious MPGs.

"Prius Eco—Isn’t That Redundant?
Of course, the big number here is fuel economy, and while the official figures are not yet out, Toyota is projecting that the ratings will come in at 54 mpg city and 50 on the highway, increases of 3 mpg (city) and 2 mpg (highway) over the current car. With weight essentially unchanged and only a small aerodynamic improvement—the drag coefficient drops from 0.25 to 0.24—this is a useful improvement. But wait, there’s more.

Toyota is also introducing a Prius Eco model that is expected to achieve substantially better mileage—try 58 mpg city and 53 highway. To achieve these results, the Eco model, more properly called the Prius Two Eco, starts with the base Prius Two model and cuts 65 pounds via various measures. A lithium-ion battery instead of the nickel-metal-hydride battery shaves 35 pounds. The rest comes from eliminating the rear wiper and from replacing the space-saver spare tire—and its attendant jack—with a tire-repair and inflator kit.
The Eco model also gets special infrared-blocking windshield glass, to reduce the air-conditioning load. And it uses special Dunlop Enasave 01 A/S 195/65-15 tires that have even less rolling resistance than the standard tires and are inflated to 39/36 psi front/rear rather than 36/35 psi."

2016 Toyota Prius First Drive – Review – Car and Driver

 

very interesting, thanks. i am eager to test drive these tyres, to see how they ride, sound and handle. also curious about longevity. are they new, or are there reviews?

if i could add 4 mpg's by losing 65 lbs, the rear wiper, and increasing tyres pressure, i would do it in a heartbeat. it must be the tyres.

disappointing that the prius product expert didn't know this little tidbit.

surprisingly fair write up by c&d.

 

"While the torque curve isn’t bad, the Prius still struggles with top-end speeds and doesn’t like downshifting when it is time to come to a complete stop."

2016 Toyota Prius Eco Review: The Hybrid Toyota Needed All Along

 

Here are all 3 reviews at TireRack.com:

Dunlop Enasave 01 A/S