2016 Prius Two MPG changed after switching 15" rims to factory 17" ones

Getting someone to divulge what specific tire they have is like pulling teeth around here, almost invariably becomes "20 questions". One thing, if the answers are vague, chances are they didn't care much, weren't specifically shopping LRR.

 

Or the 50/54/52 advertised is actually for the 17" models and the 53/58/56 is for the 15" models.

Fuelly has three 2016 Four Touring:
Based on data from 3 vehicles, 30 fuel-ups and 14,861 miles of driving, the 2016 Toyota Prius gets a combined Avg MPG of 51.16 with a 1.21 MPG margin of error.

That is not far off from the 52 combined Rating.

Compare that to the Four:
Based on data from 8 vehicles, 41 fuel-ups and 20,842 miles of driving, the 2016 Toyota Prius gets a combined Avg MPG of 57.97 with a 1.84 MPG margin of error.

That is much better than the 56 Combined.

Food for thought.

 

Based on the EPA fuel economy data file, the 50/54/52 is for a NiMH model, which can only mean the Two.

And, for the Two:
"Based on data from 3 vehicles, 26 fuel-ups and 10,726 miles of driving, the 2016 Toyota Prius gets a combined Avg MPG of 51.69 with a 4.57 MPG margin of error."

Edit: And, the Three, Four, and Tourings actually share the Eco's emissions certification, although the fuel economy data file lists both GTYXV01.8PC3 (the Two's test group) and GTYXV01.8PC4 (the Li test group) under the regular model, and the Eco is separate (as also being in test group GTYXV01.8PC4): https://iaspub.epa.gov/otaqpub/display_file.jsp?docid=36707&flag=1

 

If the 50/54/52 is for the NiMH model, then the 53/58/56 can only be for the Li-Ion models? I have the data file but do not see where the 50/54/52 is derived from. I would appreciate if you could point it out.

One of the Two's listed in Fuelly is used as a camper. Sleeping overnight with the AC on per the notes. Also, if the picture is to believed, it has 20" tires. I would consider that an outlier. The other Two's listed are 59 and 61 MPG.

 

Looking over things, 50/54/52 is what is being claimed for the models called "Prius", whether they were in the NiMH test group or the Li test group. My guess is that Toyota took the expected most popular configuration for that, which at least based on what's available in my area, is the Two, or one of the Tourings (you're allowed to do that to an extent). That's bolstered by the data file saying that the battery type is NiMH.

For the model called "Prius Eco" (which is the Two Eco trim level), they used the Li test group results for that car.

The NiMH test group consisted of a Two (ZVW50L-AHXEBA) with both summer and all-season tires, the Li test group consisted of the following cars:

Two Eco (ZVW51L-AHXBBA)
Three/Four (ZVW51L-AHXGBA) with both 15" and 17" wheels
Three Touring/Four Touring (ZVW51L-AHXHBA) with 17" wheels

Test weight for all vehicles except the Two Eco was 3375 lbs, the Two Eco was 3250 lbs.

For completeness, here's the files:

2016 fuel economy data file: https://www.fueleconomy.gov/feg/epadata/16data.zip
Test group GTYXV01.8PC3 (NiMH battery): https://iaspub.epa.gov/otaqpub/display_file.jsp?docid=36706&flag=1
Test group GTYXV01.8PC4 (Lithium batteries): https://iaspub.epa.gov/otaqpub/display_file.jsp?docid=36707&flag=1

 

Right. 50/54/52 is for "Prius" which covers both NiMH and Li. Two Eco was in a different weight class so it got it's own rating. Without a formula to convert the actual test results into the 50/54/52 rating, I was just theorizing that Toyota chose to use the lower numbers so as not to disappoint the 17" buyers and to delight the 15" buyers. It is in the realm of possibility.

More discussion here:
Prius FE Answers buried in the EPA Test Car Database | PriusChat

 

just to add a bit of data to the argument, I just had my first fillup on my new 4 Touring. I've driven Prius since 2005 so I know how to get good mileage. My first 386 mile tank (it still had about 1/3 tank left when I filled it) got an indicated 53.1 MPG with a calculated 54.08 MPG. the calculated may be a bit high since I didn't top off the tank after it clicked off. Anyway, I'm pretty impressed that I am already beating the EPA with a 4 Touring that isn't even broken in yet. Doesn't seem to be much of an MPG penalty for the 4 Touring. BTW, my car came with Yokohama BlueEarth S34 tires.

 

Thank you for all the data and analysis.

While we're hypothesizing, there is another possibility. Perhaps Toyota worked the process by getting the 2 ECO into a lower weight class so they would get an EPA-mpg flagship that people like me would pay $500 extra for. Then they (legally) lumped all the others into a single rating so that the higher level models (with goodies people want and will pay more for) would not appear to carry an EPA mpg penalty.

When I bought my Subaru Outback in 2003 a similar marketing strategy was in place. It astonished me that the AT models had the same mpg ratings as the MT ones. So people would plunk down the additional $750-$1000 for an AT thinking there would be no mpg penalty (not an issue for me because I was an MT guy since I first learned to drive). At the time I noticed that there was a difference in final drive ratio between the AT and MT models and speculated that they lowered the mpg of the MT by giving it a more rev-happy final drive (and more zip). Now I wonder if it was a matter of grouping a low-volume model (MT) in with a high-volume one (AT) in the EPA rating process.

My sense is that the manufacturers have been "working" the EPA ratings from day 1. I would expect them to do that. So I feel zero outrage that Toyota may have done so too. Even though defeat devices have been around a long time, VW's use of them does seem outrageous: that's outright illegal cheating.

Through all of this, it's important to keep in mind that EPA ratings and actual mpg on the road are two different coordinate systems.

 

Different transmissions require different tests, AFAIK.

Changing final drive ratios may not, however, depending on the ratio of vehicles sold with each option. But, that's only within a transmission type, and that's largely because of trucks offering different final drive options for towing and such.

Changing weight may not, again depending on the ratio of vehicles sold with each option (and the Two is only 5 pounds lighter than the Tourings anyway).

Edit: To be exact, per test group, if an option weighs 3 or more pounds, and more than 33% of the test group's cars are expected to have it, it must be included in the test car's curb weight calculation. And, if more than 33% of the test group's cars have a feature that affects emissions, it must be included in the test car, and if 33% or less have it, then it must NOT be included in the test car (unless it's AC, then if any of the test group has it, the test car must have it).

So, I suspect that they expected less than 33% of the cars (EXCLUDING the base Two, because that's a different test group, and even though the Two Eco was in the same test group (which I think might actually mean that it offsets the Tourings), they ran it separately anyway) to have 17" wheels. Similarly, I suspect that they expected less than 33% of the cars to have sunroofs, which is probably why you can't get a Touring with a sunroof, specifically to keep that under 33%.

Upshot is, what likely counted towards the fuel economy figures was a Two, a Two Eco, and a Three/Four.

 

According to the EPA results linked by Krousdb, this is the resumè:

City/HWY/Comb

ECO = 58 /53/56
2/3/4 = 54/50/52
3T/4T = 49/46/48 - (49,2/46,3/47,7)

I wonder why nobody has put in evidence as a table somewhere those results ,surfaced already some time ago. I bet some people would have avoided the 17"....

The experience of the thread opener, reflects exactly the differences btw 15" and 17" on FE as measured by EPA.

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I might add, as good news for the Tourings owner, that the TOYO NANOENERGY R41 17" are not LRR and not corresponding to the more expensive TOYO NANONERGY 2 , real LRR (not sold in US, as far as i'm aware).

According to the EU class, the R41 are "C" class for rolling resistance e "C" class for wet driving; the Nano 2 are instead "A" class on RR and same for wet driving. So there's room of improvement on FE going to some real LRR tire.
Very bad choice Toyota...

 

A is best for rolling resistance? And how many letters in the scale, ie: is C about halfway through the spectrum from best to worst?

Rolling resistance ratings (impartial ones) would be very welcome in North America.

 

Here's some info on Europe's tire labeling system: ETRMA - Tyre Labelling

 

They REALLY make it so you can't get to their page, it has embedded blanks.

 

In actual fact is difficult to understand how industry in NA is lobbying to avoid customer could properly compare tires.... most of the world uses already some classification method (that you can correlate btw different systems)...

Federal Register | Tire Fuel Efficiency Consumer Information Program

This is the approach:



Each RR class corresponds to a range of Rolling Resistance coefficient, taken from test on a rotating bench:



ETRMA - Tyre Labelling

What does it means in terms of FE, here a comparison taken by Autobild, on a VW Golf:

205/55 R16 results from fuel consumption at constant 60 kmh:

3.25 l/100 km (72 mpg) Toyo Nanoenergy 2 (class A)

3.47 l/100 km Conti EcoContact 5 (class B)
3.48 l/100 km Bridgestone EP150
3.48 l/100 km Hankok kinergy eco

3.56 l/100 km GY EfficientGrip Performance
3.6 l/100 km Dunlop Sport BlueResponse
3.6 l/100 km (65 mpg) Michelin EnergySaver+ (class B)

3.66 l/100 km Nankang
3.66 l/100 km Pirelli P1 Verde

 

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Good points, but regarding the 2016 Four Tourings on Fuelly, I would note that the majority of data is coming from a single vehicle. Since that vehicle is mine, I have been paying rather close attention.

Specifically, I am responsible for over 10,000 of the 14,861 miles, and something like 21 of the 30 fuel ups.

While I would not discount the impact of the 17" tires -- I am well aware of it and not happy about what I have been calling Toyota's legal fraud -- I would observe that my vehicle is located in New England, whereas many of the non-tourings are located in warmer climes.

I would also observe that my MPG has go up every month, and although temperatures remain cool, my MPGs seem very sensitive to temperature. While have not logged ambient temperature, my "gut" tells me that the relatively high 53.8 MPGs on my last tank can only be attributed to the weather.

Again, as one who is responsible for most of the Touring data, I would also add that most of my miles are on a relatively unencumbered highway and at the "speed of traffic". This morning, the display topped 60 for the first time on my 40+ mile ride to work but I was going slow thanks to traffic issues-- and it was warmish.

Again, this is not to discount the negative impact of the 17" wheels.

What bothers me more -- much more -- is my observation that my mileage really sucked in the colder weather for the first 10 or 15 miles of highway drive. Even on the coldest days I tended to reach a minimum of 50 MPG on the gauge after 35 miles or so, but had I reached my destination after just 8 or even 15 miles, my mileage would have been abysmal.

And yet, on the few 70* days we had (and are now gone) I could be getting 55 - 60 rather quickly.

Anyway, just food for thought. Someone really needs to do a regression on all the variables!

 

I think your reduced MPG has more to do with the tires being used than the rims.

LG-H901 ?

 

I have noticed a curious bimodal distribution … possibly trimodal. After my test drive of a Level 3 and the scattering of EPA roll-down coefficients, something is going on. But we saw a similar bimodal hump with the early Gen-3 data:

At the time, one working hypothesis was the difference between indicated MPG versus pump/odometer measurements but 47 * 1.06 = 49 << 57 MPG. Certainly that appears to be the case when comparing the two reporting methods:


I figured it was the difference between former Prius owners who had good driving practices and 'capture' drivers from ordinary cars but there are no identifiers.

It remains a puzzle.

Bob Wilson

 

Which 17 tire did you get? I just bought the same touring 17 wheels. I'm still undecided on putting them on. I have a 2 Eco model. I'm thinking about Michelin primacy mxm4 since they are about $100 a piece.

On my sold 13 I changed the 15 in tires to Michelin defender and I lost 2-3 mpg vs the Goodyear Oem tires.

 

Exactly. And this car so easily exceeds the stated MPG. Easily. All the time. The only time I ever come close to matching it at ~56mpg, is when I drive 90 miles to my farm. Average speed of 70mph! And even then, I get 56mpg.

My drive to work everyday is 27 miles each way. Average speed about 40mph. I get consistently above 70mpg for the round trip. Running the air. In no way is Toyota going to have a problem defending the MPG numbers it claims. There are just too many cases like mine where the mileage is massively exceeded in real world driving conditions on a regular basis.