Comparison Test: 2009 Toyota Prius vs. 2009 Volkswagen Jetta TDI

LOL! I remember when the EPA 'moved the goal posts:'

• 52 City / 45 Highway - in 2005
• 42 City / 41 Highway - today

But since then the 'hypermiler' term has been successfully defined as a style of driving:

I don't use those "techniques" but simply drive within the vehicle characteristics. When I don't know what they are, I 'do the experiment' and measure them. Then I have a road map that is remarkably reproducible ... anyone can achieve the same. For example, this evening I drove 20 miles at 75 mph and with fully inflated tires and Shell 87, got 50 MPG. With dealer inflated tires and Shell 89, I only got 49 MPG. Then over a six mile stretch at 50 mph, I got 68 MPG versus the 66 MPG in the dealer prepped 2010 Prius.

Then there is the Edmunds recent test:

Curious how their highway mileage, ~47.4 MPG, seems just a tad under the 49 MPG I got at 75 mph. Perhaps they were cruising just over 75 mph on dealer inflated tires and with a low energy fuel. Note, my data is w/o the air conditioner and I understand that area is a little 'warm.'

Bob Wilson

 

Reading through this bevy of Prius vs Jetta TDI performance data; I assume that the VW is equipped with the Six-speed DSG automatic transmission with Tiptronic® and Sport mode. Right? The Prius has the wonderful CVT trans with no slop or waiting to shift of most automatic transmissions. My area of SW PA has lots of traffic to quell any spirited driving and traffic lights too many (or too depressing) to count, a manual trans would be nuts, and yes I have owned vehicles with manual transmissions. Is this another stick vs CVT farce thread?

 

Duffer:
The VW Jetta TDI does come equipped with the DSG manual or Tiptronic (automatic) trans as you mention.. However, I fail to understand your concern regarding the transmission type, if you are using the automatic trans version in the TDI or any brand with an auto trans? The DSG Tiptronic operates in a fully automatic mode unless you engage the auto shift Tipronic mode (for those who like the shifting feature without the need of a pedal clutch).. However, if you have a pure standard trans version, then I can understand your concern.. So I guess my answer to your question "Is this another stick vs CVT farce thread?" IS NO IN MY OPINION....

 

Yep. That's the problem. The TDI owners have the arrogance to come into PC to dump on the Prius,, then say the Prius owners have an attitude problem. Number of times I've gone into a TDI/VW/Jetta forum? Zero.

Seftonm's definition of hypermiling is clearly wrong.

Good question.

Another valid one is what are the posters' lifetime miles and fuel consumption on their individual vehicles? That would say a lot more than approximations they provide for individual tests.

 

Hey ShawnClark - I am a prius owner and member of this forum since Mar 08.. Happens to be that I also have an 09 VW TDI in my household... It appears that some, not all, Prius owners are very sensitive about hearing other opinions when talking about the TDI and Prius.. Even if it may be from a current Prius owner.. As a TDI owner I am not dumping on a Prius. I own one and like it very much... It is a good car, however if you read my earlier posts I hope the readers will see that I am offering my 1st hand observations, experience when comparing the 2 vehciles... As an owner of a TDI and Prius I don't consider myself arroagant at all... Just offering some personal perspective of both vehicles to be considered by the readers of this forum... Cheers!!!

 

Not according to seftonm. He has gone through multiple winters.

I was curious how winter plays a role in your normal route. Your commute seems to be unusual in a sense that your Jetta TDI can almost match the Prius MPG. Can you describe your route in more detail?

As Bob pointed out, there are some TDI owners that get better MPG than you but majority of them got worse. I would suggest you add an entry in the EPA site. It is the only known source of mult-data point by many owners.

 

Actually I'm very curious to see a set of data showing Jetta TDI MPG vs MPH. So I looked on Google Earth around State College PA and it looks like:

• Buffalo Run Rd - relatively flat north of State College
• S Eagle Valley Rd - also seems to be relatively flat
• any others ~10 miles with relatively flat terrain

Instead of giving point reports, would you consider finding a 5-10 mile segment and running a series of MPG vs MPH runs?

The typical protocol:

1. warm up the car - at least a 20 minute drive at the target speed to get the transmission and tires warmed up.
2. cruise control set speed - removes driver variability ... if traffic requires changing the speed, discard the run so weekends are better times for these runs
3. fixed entry and exit points - so the same set of terrain is used for both
4. 10 miles is perfect but shorter is OK if the conditions show the MPG indicator has 'settled out'
5. reset MPG and trip meter on entry and read out values on exit
6. two runs, opposite directions, to normalize altitude and wind effects
7. record values at 50, 60, 65, 70 and 75 mph (as conditions permit)
8. temperature and any other weather effects, don't do it in rain
9. OPTIONAL - carry a Garmin nuvi GPS and clear the trip log so we can analyze the driving profile with GPS accurate speed and altitude data

Bring us data and we can then understand what the Jetta TDI actually does. But one-time, point reports are not terribly helpful. I enjoy the irony of a Prius owner asking Jetta TDI owners to 'bring us the data.'

Seriously, if I get a chance to rent a Jetta TDI, I will for two days just to get the data that no Jetta advocate has yet to produce. Data is not an opinion, it is a fact without emotion or any other attribute but the ability to reproduce it. It is and remains the gold standard for truth.

Bob Wilson

 

Thank you Bob. I was also thinking the 66.6 MPG TDI claim must be correlated with speed and driving conditions data.

 

A quick average of MPG from that site:

Jetta Diesel - 47 MPG
Prius - 55 MPG

66 MPG for a Jetta TDI is highly unusual so is 91 MPG for Prius. We should look at average.

Remember that Diesel has about 15% more energy than Gasoline per gallon. If you take away 15% from Diesel, you have 40 MPG in terms of efficiency.

 

I have never been to Hybridfest and one year I hope to get a chance to go there. It is unexpected that Diesels are also in the Hybridfest.

Your intent is good. All we are saying is it is misleading. Getting the maximum (peak) efficiency out of a car has little to do with real-world MPG from many owners. We should take account of how wide that peak (and near peak) efficiency window is. How often a regular driver can tap into that window?

Awhile ago, I started a thread questioning if technology is the enemy of those MPG extremists. 2010 Prius is proving that to be true. A lot of regular drivers are able to achieve 50+ MPG without trying (just turn on the ECO mode). MPG extremists can not find the "easter egg" that gets that peak efficiency. Maybe there is no easter egg but a golden egg @ 1,000 - 5,200 RPM. In another word, 2010 Prius was tuned to get the most overall efficiency rather than a peak at certain situation.

 

I remember that. We both were there when an MPG extremist (from Corolla and Accord) used highway only with 50+ PSI tire pressure were used to compare to the Prius. He then tried to justify the Prius premium cost and features.

 

Thanks, Bob. That graph sum up my previous point. 2010 Prius gives a "flat" curve. It doesn't matter how (or where) you drive it, you will get consistent near peak efficiency.

Unlike other hybrids or single engine vehicle, there seem to be no "weakness".

 

On a trip to Nova Scotia, my wife drove her 400 CI, Plymouth Fury station wagon using the mph speedometer for the posted kph. It was exciting.

At the time I didn't know the conversion factor and our maps didn't have a correction factor. IMOH, every Yankee entering Canada should have to produce a card showing 'mph vs kph' affixed to the visor and be able to answer, "What is the miles per hour when the speed sign shows 80 kph?" If they can't answer it, they have to go back until they can. Then about 3 km down the road, the Mounties should have a radar speed stop.

Bob Wilson

 

I had a colleague who was stopped for speeding in Florida, and claimed that he thought the signs were in kph, which is what he was used to. He was banking on the cop not knowing the conversion actually went the other way, and he was right, since he was let off.

 

Sorry Shawn.

While not complete, Mike's definition of hypermiling is CLEARLY right.

Please take it for what it is as it won't get any more authoritative than this.

Cheers;

MSantos

 

Hi usbseawolf2000, the full name of the event is Hybridfest Green Drive Expo. So all sorts of green technologies and green driving enthusiasts show up there. I usually just type it as Hybridfest because it's quicker and everybody still knows what that means.

Please remember that I never tried to represent 67mpg as real world driving for most people. It was a mostly highway trip with temperatures in the 70-85F range. If somebody knows how, they can tap into that window at those temperatures almost any time they want if they're on the highway. There was simply a member who was expressing disbelief at 58mpg in a TDI for a mostly highway trip. I knew that the car was capable of much more on the highway, so I shared my experience in that regard.

 

Thanks as always, Manuel

Hi Bob, I already explained to you why I come here. If you ever forget, my signature conveniently explains it at the bottom of every one of my posts.

Who said the Prius can't get 66mpg on a 2000 mile trip? I did not.

Most 2-lane highway around here are 90 to 100 km/h. Gravel is 80 km/h. It may be different in the regions that you've visited, though. But remember from our previous discussion that the Sportwagen was driven from Chicago to South Carolina and back, not in Canada.

I don't have a chart for you. But you could make one if you want. From what we experienced, I've come up with an approximation that mpg + mph = 120 for the new TDI. That is with one person in the car, 70-85F, no A/C, and running on ULSD. The driver needs to be in tune with the car's operation and needs to know how to get the most out of it, but the approximation should be close to reality for speeds from 35-70mph.

 

No it is CLEARLY WRONG. You can't disconnect the two parts without making it wrong. Both are necessary for the definition to be true.

What he stated is:

"Hyper" refers to excess, not just beating the EPA rating by a small increment. And hypermiling is the use of various techniques to maximize mileage rather than "just driving." Simply beating the EPA rating is not hypermiling. It takes both the use of hypermiling techniques and the resultant excessive mpg (for the vehicle in question) to be true.

If a car is EPA rated at 30 mpg and one is getting 31 mpg (with or without unmodified driving habits) it would be silly to call that hypermiling, yet you both have effectively defined it as such.

 

Hi Shawn, getting 31mpg in a car rated at 30mpg is indeed hypermiling. The definition Manuel and I are using is from the man who created the term and the authoritative source on hypermiling.

 

Again, I was there and know exactly the conditions which the term emerged. They are mentioned extensively in my blogs of the time. 31mpg would most definitely not be enough to qualify.

Remember, EPA estimates were higher back then too.
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