Are Stated Fuel Economy Numbers from Manufacturers Ever to be Trusted?

Yep, in almost every magazine comparison the Hyundai or Kia tested would often get the lowest observed fuel economy while having the highest EPA ratings by a decent amount. People commented on this but Hyundai/Kia defenders always claimed how those magazine tests weren't a valid comparison and that the EPA test is the final word even when the EPA only tests 15% of the vehicles (how BMW got caught with the 328i recently)

Even worse when the EPA actually tests the vehicle it still relies on the manufacturer's data such as the drag coefficient and others. The only way to keep the ratings honest is to make it extremely embarrassing to cheat such as Hyundai and Kia just did.

Before they get caught again they should drop their hp ratings by 10% also. In the same test the powerful Hyundai engines just don't deliver the performance that they should.

The situations with Hyundai and BMW are not the same. BMW didn't get "caught" with the 328. Take a look at this chart, from fueleconomy.gov:

http://www.fueleconomy.gov/feg/Find.do?action=sbs&id=32904&id=32906&id=32963&id=32964

So the 328i gets the same fuel economy as the heavier all-wheel drive 328i xDrive and larger, MUCH heavier all-wheel drive 528i xDrive, and WORSE than the larger, heavier 528i with the same drivetrain? Hmmm, something's not right...

Here's one comparing to the 335i and 335i xDrive:

http://www.fueleconomy.gov/feg/Find.do?action=sbs&id=32904&id=32906&id=33054&id=32908

The 328i gets the same fuel economy as the heavier, more powerful, six cylinder 335i? Weird, then, that the 328i xDrive gets better mileage than the 335i xDrive. You'd think the 328i should carry a similar advantage to the 335i as the 328i xDrive does the 335i xDrive. Again, something's not right...

BMW has said repeatedly they want the 328i retested so the figures go back up to where they were, which they feel are the correct figures (and based on the ratings for BMW's other models, which the government has no problem with, they have a point).

The 328i was one of the 15% of the cars audited and the EPA adjusted its fuel economy, the other BMWs may or may not have been audited. They got caught with maybe one model, Hyundai and Kia got caught with all models.

The way the testing works is that the manufacturers tell the EPA the car's drag, drivetrain loses and other parameters to set up its dynometer. It doesn't appear that the EPA checks those parameters and probabaly can't tell the difference between .27 and .28 drag coefficient or if one car has 15% drivetrain loss or 17% and these are just two of supposedly many parameters. And remember that only 15% of the models are even tested.

So it looks like Hyundai and Kia were feeding the EPA the wrong dyno parameters to use by "accident" for 3 years before it all caught up to them. BMW never went into specifics what happened with the 328i audit but you can draw your own conclusions.

Yup, making it out be as though Toyota mpg claims are lies when infact the actual company being penalized for lying has to pay out 900,000 customers (my guess is they will be former customers).

http://www.thecarconnection.com/news/1080237_2014-gt-r-hyundai-kia-dropping-mileage-claims-october-sales-car-news-headlines

Correct, the old EPA test really, really liked hybrids and gave them numbers not useful in the real world. The new one still works very well for hybrids but not as much.

Our standards are still more accurate, esp the new. Also, the Japs consistently get or beat their mpg claims, as does Ford and maybe some GMs.

Over the border, the Canadian standards say the Prius gets about 60+mpg which is a joke.

you do know there's a difference between the US and Canadian gallon right?

My Hondas consistently meet or beats advertised claims.

My E350 consistently gets better than advertised mpg, so yes I do trust mercedes benz

We were supposed to believe the liar and deceiver in chief obama so why not also believe in the EPA fair tale mpg estimates?

The obama administration is the most corrupt and anti business government in U.S. history. No wonder we have had 4 years of abysmal failure and pain.

You don't even understand how ironic your post is. THE problem is that the EPA BELIEVES the numbers that the manufacturers give them. It's that they are TOO lenient with the companies. You have it completely backwards.