EPA MPG difference between 2010 and 2011-2015?

the epa does not test vehicles regularly. they mostly allow manufacturers to submit their results, hoping that fear of penalty will keep them honest.

they also change the testing rules from time to time. all in all, it's a poorly done convoluted scheme that perfectly reflects government inefficiency

 

So the variations (in various non-PIP 3rd gen Prius model years) in mpg ratings are likely just due to evolving test procedures? That’s my hunch.

 

Can you grace us with the outlines of how a well-done, straightforward, efficient scheme would look?

 

LOL, if i could, i'd be making a life with the epa. but more importantly, the correct answer to the o/p's question would be most helpful

 

I was told by jacktheripper that it is “stupid” to compare MPG results from one vehicle to the other because ymmv.

 

Well, if you can't, maybe a little lighter hand with the "they're doing it poorly and inefficiently" business wouldn't hurt?

 

don't take it too seriously, it's just a chat

 

Sure, but that whole sort of "whatever any regulatory agency does is poorly done, convoluted, and inefficient" trope is so corrosive precisely because places like chats are where it's always getting regurgitated, always with a "don't take it too seriously" as cover.

 

That is odd. At some earlier point in time, the 2010 had the same "View Original EPA MPG" link that is attached to the 2015 here, see highlighting below. But it has now vanished.

Note that if you follow this link on the 2015, it reveals the same original EPA MPG figures still shown on the 2010. Back when the 2010's displayed numbers were downgraded, they matched what is still shown on the 2015.

Checking around a bit more, I see the 2008-2009 Prius pages also now lack this "View Original EPA MPG" link.

The EPA has been fiddling with its pages and just which original or later-adjusted scores are displayed.

 

FWIW 2015 has the revised pistons and rings (happened sometime in model year 2014), which are higher friction. I’ve noticed on Fuelly to, 2015 has a slight decrease in mpg.

 

Here is an EPA source that:

How Vehicles Are Tested
"Fuel economy is measured under controlled conditions in a laboratory using a series of tests specified by federal law. Manufacturers test their own vehicles—usually pre-production prototypes—and report the results to EPA. EPA reviews the results and confirms about 15%–20% of them through their own tests at the National Vehicles and Fuel Emissions Laboratory."

Which Vehicles Are Tested
"Manufacturers do not test every new vehicle offered for sale. They are only required to test one representative vehicle—typically a preproduction prototype—for each combination of loaded vehicle weight class, transmission class, and basic engine."

That later phrase got Ford a knuckle-rapping when they stretched it beyond reasonable modern bounds, and the EPA retested and forced a major ratings downgrade. It is one of the several things contributing to Tideland's memory to back at Post #11.

That EPA snippet isn't yet the full story, or has been abridged. I'm remembering an intermediate step where all the older models, including 2008-2010, were displaying downgraded numbers on the EPA's Compare Side-by-side page. In fact, I wasn't yet aware that the 2008-2010s were now back to showing their original labels until you pointed it out with this thread.

 

There was lots more than that. Scroll down to the Ford section of this page for a 'sanitized' description and list of models affected and new vs old numbers. Some revisions were quite substantial:

Fuel Economy Label Updates

Numerous other brands were caught on 'problems' too, scroll around that page for the others.

 

no worries, i am not to be trusted

 

^ ... even when he is right, as he was this time.

 

Just in case anyone cares, here's the real world fuelly numbers for the Gen 3 Prius:

2010: 44.4 mpg
2011: 44.9 mpg
2012: 46.0 mpg
2013: 45.2 mpg
2014: 45.1 mpg
2015: 43.6 mpg

4th Gen: 50+ mpg each MY

 

I don't have a good reason why that would be, but will note that the EPA numbers have always been BS estimates. My mileage has never come close to EPA ratings. It's closer to Consumer Reports' controlled testing ratings, which I've found to be optimistic.

In 2008, I bought a 2009 Prius Touring Edition. It averaged 42 REAL* MPG over 176,000 miles. Low was 32 MPG (going 76 MPH for 10 hours on I-95, fully overloaded by 400 pounds, with a roof rack and Sears X-Cargo on it!). High was 46 MPG on a 55 MPH country road in the Fall with HVAC turned off. *REAL means those numbers are calculated manually. And no, I'm not a hyper miler. I drive without regard to saving fuel, and I set the HVAC as needed to remain comfortable. We bought our Prii to save money, not to change our driving habits. (We have six Toyota-built hybrids in our extended family!)

My 2010 bought used in 2018 gets around 40 REAL MPG average. Low is 38.5 in Winter, and high is 45MPG in summer. The car has 82K on it. Others I know with the same car get maybe 2–3 more MPG. (My son had the exact same 2010 Pack IV for a while, but with standard tires instead of the 17" wheels I have. My sister-in-law had one like that, too, before she got a 2021 RAV4 Hybrid. They got 42-43 real MPG.)

My son's 2013 Lexus ES300h is rated for 40, but gets 36 REAL MPG.

We can't complain... But we look forward to BEVs in our future.