http://www.dieselforecast.com/Articl...?articleID=487

Is it true that the EPA is overly hard on diesels? If true what is the specific reason? Of course people beat the EPA numbers in gassers and diesels everyday around here.....The newer numbers are a really easy target. Still, do diesels take a bigger mpg hit than gassers?

 

The EPA numbers are 'hard' on all vehicles. For example, the NHW11 model, 2001-03 Prius is now listed with a combined 41 MPG yet 90% of them now meet or exceed that number. Similar numbers come from the other hybrids.

Apparently the diesels now have to take the "cold CO" test that was not required before. This would reduce their EPA ratings. Then there is the diesel premium at the pump.

Bob Wilson

 

To test this out I looked at the latest EPA figures and numbers reported in Europe (www.vcacarfueldata.org.uk). I referenced vehicles in the article: a 2009 Jetta Diesel and non-diesel (2.0-turbo). And since Bob mentioned the Prius I looked up that car and similiar sized non-hybrid the Toyota Matrix (Verso). I tried several other cars but the engine options didn't match those in the US. The Euro numbers are Urban and Extra-Urban which loosely translates to City/Highway. For the US numbers all are 2009 manual transmission except the Prius (2008 CVT).

Jetta DieselJetta 2.0-Turbo GasToyota PriusToyota Matrix(Verso) 1.8 GasWith these numbers it looks like the bias is against VW more than just diesels.

 

The EPA admits that diesels achieve better real-world mileage than the official EPA ratings -- 4.3% better than the 1985-2007 ratings and 18.3% better than the 2008+ ratings. See page 8 of this report:

http://www.epa.gov/fueleconomy/420r06017.pdf

Basically, the new 2008 EPA ratings underestimate the true MPG of all vehicles now, but now hybrids suffer the least (i.e. for hybrids the new EPA ratings are closer to what people will actually get, especially compared to the highly overestimated pre-'08 ratings) while diesels suffer the most.

 

The important comparison isn't between the EPA test (or any other test) and real world but relative comparisons between vehicles. If you consistently do X% better than EPA with one vehicle, chances are you'll do X% better on another vehicle.

The EPA only acknowledges that the 60 or so owner entered MPG entries for the diesels is 18% higher than EPA. Considering the attitude of diesel owners and fans, I would expect they cherry picked or otherwise inflatted their MPG numbers to protest the EPA "conspiracy" against diesels. In other words, it's not data and certainly not objective.

Objective, head-to-head, apples-to-apples tests, such as the recent Edmunds test, give numbers that should be compared in a relative sense.

 

The same could be said of hybrid drivers regarding the cherry picking data. That 100+ page EPA PDF is pretty convincing.....

 

You can more validly state that the people who are posting their mileage data to the EPA site are specifically those who are interested in fuel economy and therefore are more likely to drive in an economical manner. The average Joe Schmo who just pumps $20 worth of gas into his tank at a time wouldn't even be able to post his mileage figures even if he wanted to.

Speaking of which, I find it surprising -- or maybe not -- just how many people never, ever fill up their tank; they just always go by fixed dollar increments. You'd think that would be less prevalent here in NJ, where mandatory full-serve removes the hassle of pay-before-you-pump (which is one thing my family and I can never quite get the hang of when driving out-of-state)... but I still see it a lot.

And for those who do fill up, it seems that they are much more likely to judge a vehicle's fuel efficiently merely by how much it costs them to fill up, versus the actual MPG it gets. Whenever I mention my Passat TDI and the mileage it gets, the MPG figures seem to just go over their heads, and instead, they always ask me how much it costs to fill up. With its large 18.5-gallon tank, they are shocked and disappointed to hear how much it costs me to fill up -- until I tell them that tankful is good for 700 to 800 miles of driving, versus the typical 250-350 miles for a gasser with an average-size tank.

 

Hi,

The report table is a little ... bland:
This graph shows more clearly what is going on based upon http://www.fueleconomy.gov/ user and model data:

The relative 'sandbagging' from the EPA numbers means 2006 Jetta, the middle 90%, all exceed the EPA numbers. In contrast, the 2006 Prius owners have only the lower 1/3d falling below the EPA estimate. Of course there is another way to look at it:

• 66% of the Prius owners get a hypermiler star
• 100% of the Jetta owners get a hypermiler star

Congratulations diesel owners!

Bob Wilson

 

The average for the 2008 Prius owners is dead on the 46 MPG EPA number. So the new EPA numbers seem to be on the mark for non-diesel and hybrid vehicles.

The real question should be how the same government that gives tax credits for buyers of $80K Toyotas (aka Lexus) getting 20MPG. Also put emission laws in place removing diesels from the US market for 2 years! Even the EPA uses the word "may" in describing the issue with NOx emission. Fortunately, in the liberal environmentally conscious land of $8/g fuel! The Europeans have continued to push Diesels forward. I guess the Toyota lobbyists don't have any leverage there.

 

Toyota hybrids have not gotten a tax credit since September of 2007. Worse, the credit didn't work if you were in the AMT tax bracket. So do the "liberals" get your apology? <grins>

Bob Wilson