Popular Mechanics: Jetta TDI outdoes Prius in mileage test, kinda
There's a question that's sure to be on the minds of many of our devout readers: does the new Jetta TDI come close to the Prius when it comes to fuel mileage? We've had our first impression, and we'll see for ourselves soon enough when we get our hands on a new TDI for a long-term test, but Popular Mechanics has done some of the footwork for us already. In a test that wound its way both through California's inner trenches - the surface streets in LA *shudder* - along with some a good deal of snaking blacktop in between, the crew at PM kept separate logs for both city and highway mileage, all the time with a view towards fuel mileage. So, who won? Um, depends.
The Jetta bettered the Prius by less than one mile per gallon on the highway, as it rode its abundant torque to a mild victory. In the city, which is the traditional edge for the all hybrids, the Prius earned its fuel mileage crown back by besting the TDI by over ten miles per gallon. Plus, diesel fuel still costs a bit more than regular unleaded. That's not the whole story, though, as PM still preferred to spend time in the Jetta's interior. So, which do you choose? Why not tell us yourself in the comments.
[Source: Popular Mechanics]
Reader Comments (Page 1 of 2)
meme 11:54AM (9/25/2008)
For the 812,394,823th time, although it never seems to sink in anywhere, *gallons of different fuels are not directly equivalent*. Diesel is 15% denser than gasoline. You're consuming 15% more petroleum per gallon and releasing 15% more CO2. Hence, if they tied in terms of miles per gallon on the highway, the Prius won by 15%. If the Prius consumed 75% as many gallons of fuel in the city, the Prius actually consumed 65% as much petroleum by weight and released 65% as much CO2. Oh, and to top it off, the Prius is a SULEV vehicle; the Jetta is LEV.
This whole "all gallons are the same" notion is just ridiculous. Hey, beryllium is a much more energy dense fuel than gasoline. Could I get kudos for running a car on a beryllium slurry and getting 150mpg?
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Zigster 12:01PM (9/25/2008)
Hey, beryllium is a much more energy dense fuel than gasoline. Could I get kudos for running a car on a beryllium slurry and getting 150mpg?
if person A can run as far on whole milk as person B does on skim milk, would I let you mention person C who drinks only cream? hell yes.
slk23 12:47PM (9/25/2008)
It seems like much of your objection is pedantic. What difference does it make that diesel fuel has 15% more BTUs than gasoline? From what I understand the number of diesel gallons compared to gasoline produced from a barrel of crude oil depends on the process. I've also heard that the refining process for gasoline is more energy intensive than it is for diesel, although that may not be the case now with ultra-low sulfur diesel.
For the driver/citizen, the relevant factors are:
Cost of fuel.
Emissions (CO2 and pollutants).
Driving enjoyment.
I'd prefer to drive a car that produces as few emissions as possible, but I wouldn't mind spending a little more for fuel if the car is more fun to drive. Personally, I'm on the fence concerning hybrid vs. clean diesel.
meme 1:11PM (9/25/2008)
"I've also heard that the refining process for gasoline is more energy intensive than it is for diesel, although that may not be the case now with ultra-low sulfur diesel."
Your assumption is correct; it no longer is the case. I have this on authority from a president of an oil supermajor.
Backing up, we have:
1) One gallon of diesel fuel contains 15% more petroleum
2) Burning it releases 15% more CO2.
Summary: they are not directly equateable.
"For the driver/citizen, the relevant factors are:
Cost of fuel." -- Last I checked, diesel averaged $4.059/gal. Gasoline averages $3.648/gal. That's 11% more expensive.
"Emissions (CO2 and pollutants)." For a gasoline car and a diesel that get the same miles per gallon, the diesel car emits 15% more CO2 (as discussed above). Hence, the Jetta TDI is emitting about 15% more CO2 on the highway and the Prius is emitting only 65% as much in the City. As for other emissions, SULEV requirements are far stricter than LEV requirements.
"Driving enjoyment." Well, this one is at least subjective. :)
slk23 1:57PM (9/25/2008)
Meme:
"1) One gallon of diesel fuel contains 15% more petroleum
2) Burning it releases 15% more CO2.
Summary: they are not directly equateable."
More CO2 is less desirable, but compared to other transportation factors the difference is not particularly significant. The other smog-producing emissions worry me more.
You may not be willing to pay $500/year more for fuel, but I would if the car gives me more pleasure than a Prius (for example). I'm no Prius basher; they are good cars. But I don't drive a lot, and when I do drive I like to enjoy my time doing it. My vehicle must to be an enjoyable drive, and I'm willing to make a reasonable compromise to get that. My opinion, and that of every car reviewer I've seen, is that the Prius is commendable is many ways but it doesn't rate high on sportiness (or Farfugnugen :-} ).
I'm hoping that the Honda Insight (II) will be more agile and fun to drive than the Prius. VWs rate high for driving experience but I don't trust their reliability in spite of recent improvements. I speak from experience: I love my '89 GTI but it's not quite a Honda or Toyota when it comes to reliability.
wxman 3:10PM (9/25/2008)
meme - the 2009 Jetta TDI has been certified ULEV II by CARB and is near or below SULEV for all regulated emissions except NOx. Plus there are essentially no direct or indirect evaporative emissions from diesel fuel like there are from gasoline.
I'm still not convinced that ULSD is as energy-intensive in refining as gasoline. I think I've already referred you to a UC-Davis paper ( http://www.its.ucdavis.edu/publications/2003/UCD-ITS-RR-03-17-MAIN.pdf - pages 93-96), which asserts that while ULSD requires more energy to refine than conventional diesel fuel, it's still lower than gasoline.
Also, ALL WTW studies I've seen have lower energy inputs for diesel fuel than gasoline (well-to-tank), and another life-cycle energy model, ANL's GREET model, also has lower energy inputs for diesel fuel.
meme 5:36PM (9/25/2008)
"I'm still not convinced that ULSD is as energy-intensive in refining as gasoline."
Well, you have a paper from 2003; I have a president of an oil supermajor from a couple months ago. I'll go with the latter. You can go with the former if you choose.
Snowdog 6:08AM (9/26/2008)
You are fighting about minutia. If you could have a car that was otherwise identical and got 40mpg and you could choose if you got it from regular gas or diesel, anyone in their right mind would chose gas.
Gas is cleaner both in burning and in the crap that sticks to your hands when you fill up. Gas is cheaper across North America. Gas is much more widely available across North America.
But they didn't get the same mileage. They are tied on the highway and the Prius pulled way ahead in the City.
On the numbers it is a clear Prius win over the diesel Jetta.
Diesel fans/Hybrid haters will have to go back to insults: not as fun to drive, looks funny comments, because on real world economy they are in the back seat.
JD 11:55AM (9/25/2008)
I have a Jetta TDI because I was concerned about the cost of replacing the batteries in a hybrid and I can burn biodiesel as an option (it actually runs better on it!). Also, oil burners have a long history of reliability in Europe. Now if they could just get the rest of the car to last as long as the engine...
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PeterG 12:26PM (9/25/2008)
The battery is ~$2500 today and likely much lower in the at minimum 8 years you might to need to replace it. 10 Years in California.
Even including that I bet the Prius maintenance is lower.
You are talking about a Toyota, with a normally aspirated gas engine with a timing CHAIN, with no transmission requiring maintenance. In short other than the battery, this is actually a very mechanically simple, robust and low maintenance system.
Vs A VW with TURBO, with timing belt (lots of expensive timing belt changes from VW) and a transmission. A lot more mechanical to go wrong.
Even if I had to replace a toyota battery, it would likely be a long way ahead on maintenance costs.
As far as Bio Diesel. What difference does that make even if you could burn a significant amount? VW only allows B5 at the moment. That is 5% biodiesel. These are not the old smokers with low tolerances that could burn anything and belch it out the back. These are new highly tuned, high precision with ultra high pressure injectors, extensive pollution controls and particle traps. You won't be dumping fryer grease in this one.
PeterG 12:13PM (9/25/2008)
Prius scores a knockout in the city (Prius wins by 12.7mpg).
It is a virtual tie on the highway (Jetta wins by 0.6 mpg).
This is a Jetta Win?? It is a clear Prius Victory before you even factor in extra cost, lower availabilty of diesel (and the extra stench if you do your own fillups).
This is not the TDI of old, it doesn't beat the Prius on the highway, it merely ties it and in the city the Hybrid cleans up as expected.
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Wise Golden 1:03PM (9/25/2008)
I like both, but experience tells me to stay away from Eurojunk and go with the Prius. The $1800 sensor, and the $400 headlight on my Mercedes taught me that lesson.
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Throwback 1:23PM (9/25/2008)
As someone who actually likes to drive, the Jetta would be my choice by a mile. I am still waiting for a fun to drive hybrid. Honda CR-Z perhaps?
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Sree 1:36PM (9/25/2008)
Why dont they just marry both the Technologies TDI + Hybrid on Li-Ion with Plug in capabilities and thin film solar to recharge the batteries on the run and fuel as Bio diesel..
Most of your energy problems will be solved .. finally free from Oil from the Gulf. Its very much doable I would love to own a car like that
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bohdanz 1:35PM (9/25/2008)
The comparison by Popular Mechanics downplays the reality of gas v diesel prices.
I live in Los Angeles, where diesel is easily 40 cents a gallon more than regular fuel, which is all the Prius needs. Diesel 'still costs' a bit more? It always will.
And that's why hybrids will continue to be the better choice when it comes to dollars and cents.
Bohdan
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fnc 1:37PM (9/25/2008)
I don't generally complain about misleading headlines but dang, that one takes the cake.
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Mike Z 2:43PM (9/25/2008)
Isn't the Camry Hybrid a better analogue for the Jetta?
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rob 3:55PM (9/25/2008)
If I buy the VW, do I have to also get their quality? Perhaps I should just buy two and use one for parts? Nahh...I'll go with Toyota.
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Mark Derail 4:43PM (9/25/2008)
I went with the Prius, two years ago.
Now imagine this...in three more years it's paid for.
Then one extra year to pay for the EV-10 (or 20 or 30) upgrade, that will give me FULL electric use, a plug-in, and if I run out of juice, the ICE will not only kick in, the "extra" energy generated by the ICE will charge up the batteries.
(Pricing on Prius EV-Kits keep dropping every year)
So, over the span of 6 years, I have a decent EV car that is highway capable.
Upgrading a Jetta TDI to be able to do EV-mode, would cost how much?
If you don't get a hybrid asap, you'll be left behind along with millions of car owners desperately trying to get EV's and hybrids, out of assembly plants barely able to build 30k units a year.
Hell, the Prius can also be fitted with CNG, there's more than enough room in the back to house a 100lb tank.
Tri-Energy capable future-upgradeable car.
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slk23 2:51PM (9/26/2008)
Snowdog:
You're right if you're only focused on the cost of driving the vehicle. The point I (and others) have made is there is more to driving than saving a couple pennies. The torque of a diesel and the handling of a Jetta compared to a Prius are important enough to some people and they are willing to spend a little more for it. That's not unreasonable -- it just a matter of how you rank your priorities.
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