From www.fueleconomy.gov data:

2006 Volkswagen Jetta TDI diesel
Manual transmission: "New" vs. "Old" EPA MPG Estimates
User rating (based on 51 owners) is 27% higher than "new" EPA estimate and 10% higher than "old" EPA estimate.

Automatic transmission: "New" vs. "Old" EPA MPG Estimates
User rating (based on 49 owners) is 23% higher than "new" EPA estimate and 7% higher than "old" EPA estimate.

 

Darn, that really puts the diesel advocates in a hurt. Not only do the EPA mandated numbers make them look bad but the current $/gal. adds insult to injury. In the meanwhile, the small sample set of users at the EPA web site, a place not posted on the vehicle windows, says something else ... bad luck.

Still this isn't enough to tempt me until a diesel hybrid comes out like one of these 2001 models:

• The 80 mpg diesel-hybrid GM Precept
• The 72 mpg diesel-hybrid Ford Prodigy
• The 72 mpg diesel-hybrid Chrysler ESX-3

So welcome to the "nobody believes me" club. For years, hybrid reviewers were quite willing to say, "Nobody gets hybrid EPA numbers" while I stared at 52+ MPG that exceeded the EPA numbers. Heck, I even bought a vanity plate, "C-52MPG." Now diesel advocates have to depend upon pro-diesel writers who have to write around both the official EPA numbers and current diesel prices.

BTW, I'm not one of these hypermiler advocates. I started my hybrid ownership by plotting MPG vs MPH:


Good luck!

Bob Wilson

 

Thank you for the great reference!
I had forgotten that they continued to capture user reports. So I loaded the 2006 data for the Jetta and Prius automatics. I also setup the spreadsheet to drop the upper and lower 5%, the outliers, to plot the average of the middle, 90% of all users:

After we take out the lower and upper 5%, the outliers, we find respectable averages for both vehicles. However, the Prius owners seem to have a wider range, suggesting there may be ways to significantly improve performance. This is why I find the study of my Prius, even two and a half years later, still fascinating.

So for new buyers, a chart like this and the price of fuel lets them make informed decisions on the likely operational costs. But like I mentioned earlier, I'm really looking for the diesel-hybrids.

Bob Wilson

 

Bob,

I completely agree with you, only from the other side of the issue (I'm not really tempted by hybrids until diesel hybrids are available, if that ever happens, higher diesel fuel prices notwithstanding).

The U.S. government poured in untolded amounts of money through public-private sector CRADAs for PNGV, and all it turned out to be was an expensive lab experiment.

The Big 3 actually produced working prototypes of these PNGV diesel-hybrids. And this was with 1990s technology. Supposedly, the auto companies felt the technology was too expensive, although they continue to pursue incredibly expensive fuel cell vehicles (go figure). Dodge was able to bring the cost penalty down to about $7500 with their ESX3 ( http://www.popularmechanics.com/auto...51.html?page=2 ). According to ANL, diesels actually get more benefit from "hybridization" than gasoline engines (although less benefit from engine downsizing).

By the way (I meant to mention this in my previous post) - we achieve the 47.2 mpg average with our Jetta TDI almost exclusively on B20.

 

It is nice to have reasonable diesel folks in our midst. A lot of us are excited about an eventual diesel hybrid. That should bring the camps closer together.

Don't let the haters run you off. You don't need to drive a hybrid to post here. Any reasonable pro-diesel talk is generally welcome.

There are some diesel folk that have ripped on hybrids and hybrid drivers so it natural that some here will be a little defensive...Myself included somedays.

 

BigTuna - thanks.

I am well aware that there are many diesel proponents who tend to bash hybrids. I'm not one of them. I applaud anyone who tries to decrease their person fuel consumption.

I really don't understand the rational for arguing against more choices, from either side. Everyone should be happy with more hybrid AND diesel choices, or one would think anyway...

 

It was this program that inspired both Honda and Toyotas to develop their hybrids. The only difference, they made and sold theirs, quite successfully.

The PNGV budget was poured, continues to pour, into the hydrogen fool cell programs.

It turns out that a hybrid drivetrain opens the range of engine options more than most folks realize. For example, the Chevy Volt could use a Stirling engine or even a regenerative, micro-turbine. The Stirling, an external combustion engine, could run on coal or even sawdust/wood pellets.

Bob Wilson

 

I'd like to see how the Chevrolet Cobalt XFE would've done in Edmunds' test. It is the new economy-oriented version of the Cobalt, available only with a manual transmission and boasting a class-leading 36 MPG highway. GM claims that with low-rolling-resistance tires, gearing changes, and other unspecified tweaks, they were able to improve the Cobalt's milage from 24/33 city/highway MPG (27 combined) to 25/36 city/highway (29 combined) without reducing the engine's power output. A Pontiac G5 XFE version will reportedly also be available, but has not officially been announced yet.

And as a whole, there is little fanfare but much merit in simply choosing a traditional base-level, gasoline engine, manual transmission economy car, rather than going for a hybrid or diesel with the hope of making up for the increased initial purchase price with fuel savings over time. And that does not imply a cramped, tinny econobox; although the EPA figures indicate otherwise, my Mazda3 2.0i has actually been giving me better mileage than the Kia Rio5 I had previously, despite being a bigger car with a lot more power.

Here are the 25+ MPG contenders, going by the 2008 EPA city/highway and combined ratings (or 2009 models where indicated), all assuming the base level engine with manual transmission:

make/model: city/highway MPG (combined MPG)
Smart fortwo: 33/41 (36) Premium (automated manual)
MINI Cooper: 28/37 (32) Premium
Toyota Yaris: 29/36 (32)
Honda Fit: 28/34 (31)
'09 Toyota Corolla: 26/35 (30)
Chevrolet Cobalt XFE: 25/36 (29)
Pontiac G5 XFE: 25/35 (29)
Honda Civic: 26/34 (29)
Scion xD: 27/33 (29)
Hyundai Accent: 27/32 (29)
Kia Rio/Rio5: 27/32 (29)
Ford Focus: 24/35 (28)
'09 Pontiac Vibe: 26/32 (28)
'09 Toyota Matrix: 26/32 (28)
Nissan Versa: 26/31 (28)
Hyundai Elantra: 24/35 (27)
Chevrolet Aveo/Aveo5: 24/34 (27)
Mazda Mazda3: 24/32 (27)
Saturn Astra: 24/32 (27)
Nissan Sentra: 24/31 (27)
Kia Spectra: 23/30 (26)
Dodge Caliber: 24/29 (26)
'09 Mitsubishi Lancer: 22/30 (25)
Suzuki SX4: 22/30 (25)

 

My experience with TD vehicles have been that they tend to give good economy overall and the potential to give excellent fuel economy if driven in the exact sweetspot for the specific vehicle. For most TD's it is a speed at which the engine does not have to work too hard in top gear, typicaly around 55MPH. It is also important to keep speed and throttle constant to gain excellent mileage.

On my most recent trip I drove over 4000 miles with a Land Rover LR3 TD (2.7L V6 TD). It averaged 23 MPG overall which is not bad at all for that size vehicle, but it was able to do well over 30 MPG for stretches where the road was flat and adn I kept speeds at 55MPH. Unfrotunately as with most TD engines power range was an issue, which made overtaking much more involved than it should be.

This echoes my experience with varies TD's I have driven in the past from VW, BMW, Audi and MB.

My point being that although TD's can achieve excellent mileage, very few actual users will actually achieve that due to driving style and driving conditions. The most vocal TD supporters that actually achieve excellent mileage neglect to point to the very specific operating conditions of their vehicles.

For most users with my type of uasge and commute a good hybrid makes much more sense (70% highway with typicaly CA highways that turn into parking lots for 20-30% of the highway miles, lots of hills, 70-80 MPH cruising when it actually moves, and the rest 2-3 mile trips). My Prius II still manags above 49MPG in these conditions and I doubt any currently available diesel sedan will even get 40MPG with this usage pattern.

I think Consumer Reports mileage tests best shows what the average guy on the block can expect from vehicles, vs what the extreme can achieve in limited usage patterns and with extreme care in driving.

CR listing for 2006 DSG 1.9TDi with 6 spd DSG (much better than conventional auto) (Keep in mind these numbers are still excellent for the average vehicle)
Overall - 34MPG
150mile trip - 41MPG
CR City/Highway - 24/46MPG

Camry 4 cyl 5spd Auto
Overall - 24MPG
150mile trip - 29MPG
CR City/Highway - 16/36MPG

Camry Hybrid CVT
Overall - 34MPG
150mile trip - 37MPG
CR City/Highway - 28/41MPG

Prius II
Overall - 44MPG
150mile trip - 48MPG
CR City/Highway - 35/50MPG


This shows that the diesel can get similar results to the Camry Hybrid.

Unfortunately what worries me is that most diesel manufacturers are aiming to only meet the minimum T2B5 emissions regulations, while most of the hybrids are well ahead of that standard. Also keep in mind that if a diesel uses the same amount of fuel as a hybrid it still prodeces 15% or so more CO2, apart from the additional air pollution. Just something to keep in mind.

 

Thanks,
I plotted the data to give some insights:

What I find interesting is the CR numbers consistently show worse City versus Highway mileage. This makes most sense if CR is only 'cold starting' with pretty much max accessories compared to the EPA testing protocols.

Bob Wilson