Hypo-miling redux: Toyota Prius vs Volkswagen Jetta TDI
Back in June we told you about a test that Top Gear did with a Toyota Prius and BMW M3. At the time, the Top Gear crew ran a Prius around their test track as fast as they could for 10 laps with Jeremy Clarkson pacing right behind it in a BMW M3. Not surprisingly, the Prius - which is not designed for this kind of application - scored a comparatively poor 14.3 mpg (U.S.) in the test. As we all know, driving style does affect mileage which we again demonstrated this week during our drive of the Jetta TDI. The driving we did in the southern California canyons was at least as strenuous what Top Gear did to the Prius and we managed a much more impressive 30.7 mpg. While the Top Gear air field track is flat, the Jetta drive route included significant and repeated elevation changes as well as a 20 degree temperature swing from about 73 along the coast up to over 90 further inland. Altogether, a very impressive performance by the German diesel even without any start stop or hybrid capability.
Photos Copyright ©2008 Sam Abuelsamid / Weblogs, Inc.
[Source: AutoblogGreen]
Reader Comments (Page 1 of 2)
Jack S 12:13PM (9/19/2008)
Impressive score from Toyota Prius. looking forward to buy one very soon. http://www.buyingadvice.com/toyota-corolla-2007-review.html
Reply
Darrell 12:15PM (9/19/2008)
yeah, diesel is just better technology, put biodiesel in it, and you get way less pollution than a prius could ever hope for, in all counts of pollution, not just co2.
Reply
LaughingMan 1:46PM (9/19/2008)
First of all, I don't recommend putting high percentage mixes of biodiesel into a new Jetta TDI. That's a good way to destroy the particulate filter, and violate your warantee. Before you do anything like that, talk to an engineer at VW. They'll tell you it's very risky.
Secondly, exactly what class of emissions does the TDI do better than the Prius?
The Jetta TDI is a LEV II vehicle. The Prius on the other hand, is a SULEV II. That's 90% fewer particulates and NOx than the LEV II.
If you use biodiesel instead of petrol-derived diesel, the NOx worsens, not improves.
Just about the *only* area where a diesel vehicle matches the Prius is CO2 emissions, and that's purely a function of fuel economy. A Prius which gets about 48 MPG will have the same CO2 impact as a Jetta TDI that gets 48 MPG... But the Prius will have significantly lower NOx and particulate emissions because gasoline simply burns cleaner than diesel with respect to NOx and particulates. That and it's easier to scrub for NOx using the catalytic converters in gasoline vehicles in general.
Check your facts before you claim that any diesel emits less pollutants (other than CO2) than a Prius.
meme 4:35PM (9/19/2008)
"A Prius which gets about 48 MPG will have the same CO2 impact as a Jetta TDI that gets 48 MPG"
No it won't. Burning a gallon of diesel emits 15% more CO2 than burning a gallon of gasoline. It's a denser fuel. Prius even wins in that regard.
One should never directly compare diesel MPG figures with gasoline MPG figures. They're not the same fuel.
wxman 11:39AM (9/23/2008)
The 2009 Jetta TDI has been certified ULEV II in California ( http://www.arb.ca.gov/msprog/onroad/cert/pcldtmdv/2009/volkswagen_pc_a0070279_2d0_u2_diesel.pdf ).
The CARB-certified SULEV II Prius actually has higher (more than 50% higher) HC emissions than the Jetta TDI when taking vehicle evaporative emissions into account (diesel fuel is essentially non-volatile). And that doesn't include the higher "ancillary" HC emissions from the distribution and storage of gasoline (i.e., indirect HC emissions). HC is the problematic emission with respect to ground-level ozone ("smog") formation, not NOx.
The certified emission of PM from the Jetta TDI is 0.001 g/mi, 90% less than the SULEV certification level.
Just because a particular line of vehicle doesn't neatly fit into a contorted regulatory "emissions box" doesn't NECESSARILY mean that it's "worse" from an air quality perspective.
PeterG 12:26PM (9/19/2008)
"The driving we did in the southern California canyons was at least as strenuous what Top Gear did to the Prius "
You flogged it as hard on public roads as someone going flat out on a track? I call shenanigans on that.
Reply
flabby 1:13PM (9/19/2008)
Quote from Jack S:
"Impressive score from Toyota Prius."
Um...Jack, the prius got 14.3 mpg and the Jetta TDI got 30.7 mpg. In what way was the Prius's score "impressive" in this article? Maybe you're being sarcastic?
Reply
Chris M 6:37PM (9/20/2008)
Um, flabby, that "14.3 mpg" was from a bizzare and rigged "test" by Top Gear, where the Prius was driven at maximum speed (about 120 mph) and any car would get lousy milage at that speed - unless they are drafting close behind another car, as the BMW M3 in that Top Gear test was. Nor is it fair to compare that "14.3 mpg" driven at high speeds to a drive at much lower speeds under different conditions.
The worst milage I ever got in my Prius was 36 mpg, on a 110 degree day with the A/C running full blast, and that is still better milage than that Jetta running under cooler conditions. Runs over the Altamont pass routinely gets me 50 mpg.
Benjamin Jones 1:38PM (9/19/2008)
I don't see how racing could compare to hills at all. There are no long coasts where almost no fuel is used on race tracks, ;)
Reply
LaughingMan 1:50PM (9/19/2008)
I agree. It's an unfair comparison. Unless the Jetta TDI was zipping around at 100 miles per hour with the throttle wide open the whole time (which is unlikely knowing Southern California)... the comparison is totally bunk.
Dave 2:40PM (9/19/2008)
Just a few comments:
Great, more Prius bashing from a supposedly "Green" blog.
Great, another totally invalid comparison. As others have already said, there is absolutely no way that aggressive on hilly backroads driving even comes close to driving on the track.
Track driving involves mostly alternating between wide open throttle and full braking.
Aggressive backroads driving is a lot less demanding given that you typically have at least some traffic to deal with and that you would never push as hard as possible on a public road because of safety and legal concerns.
BTW, LaughingMan, nice post earlier, but a slight correction: diesel has about 13% more CO2/gallon than gasoline, so if a diesel and a gas car get the same miles per gallon, the diesel car emits about 13% more CO2 per mile.
I swear that AutoblogGreen posts just for the sake of posting half the time. Perhaps they're just trolling for comments and page views.
GreenCarCongress.com presents a lot less bias in their posts.
Reply
LloydChiro 6:18PM (9/19/2008)
Well, Dave,
Let's face it. The Prius sucks.
JamesWB 8:41AM (9/20/2008)
Aren't diesel engines always on 'WOT'?
Snowdog 10:34AM (9/20/2008)
"Great, more Prius bashing from a supposedly "Green" blog."
It is pretty hard to take ABG seriously as a green blog. Unless it is green as in AstroTurf.
There is hefty amounts of hybrid bashing, plenty of E85 cheer leading. Even posts of GM propaganda video as straight material. Then there is featured columnist Gary Witzenburg, petrol lobbyist, professional global warming denier.
I really should get a sign up on Green Car Congress, I only post here cause I was lazy and one sign up gets me in Autoblog and here...
Sean 2:42PM (9/19/2008)
I'm definitely interested in the newer cleaner diesels, and hope VW can get it's quality issues under control. These are neat cars. But, um, this article is a little absurd.
Why is it titled 'vs'? As far as I can tell, you drove the Jetta. Through a VW-planned course. And then wrote an article about how you got about 30mpg in the Jetta.
Then there was a brief reference to Top Gear flogging a prius around a flat track at WOT. You're comparing apples to jettas.
Someone go drive an Autoblog prius around the same mountain course and get back to us with the MPG. I am not making any predictions, but it would be good to have a number, so you can make good on your 'vs' claim.
Reply
Sean 2:51PM (9/19/2008)
Is VW becoming a big advertiser for the ABG family of blogs?
There's almost a complete lack of serious content about the energy source and power plant.
Diesel engines are a fine technology with good performance in certain applications. Atkinson cycle petrol engines perform well according to other parameters. There's hardly ever any treatment of this or even recognition of this in the posts.
Some ABG content is just pointless fanboyism or posting-for-posting's sake, which is why it is more of a fluff blog than an actual source of automotive information.
OMG a celebrity sat in a concept car! Post to ABG!
OMG, a TDI car broke 40mpg! Post to ABG!
Reply
EJinID 3:06PM (9/19/2008)
Let's get a valid comparison.
Have someone at AutoblogGreen run a Prius along the same trip taken with the VW and compare the results.
Apples to Apples people...
Reply
Jim Stack 3:08PM (9/19/2008)
I get 60+ mpg in my 2005 Prius everyday. I signed on for the A123 plug-in option and then I will get 100+. I figire I'll get about 150 mpg.
That still doesn't beat my bicycle which gets over 2,000 mpge. It's the most efficient vehicle every made.
Reply
meme 4:35PM (9/19/2008)
Not when you consider the extra calories you're eating, it isn't. Human beings are inefficient at turning food calories to kinetic energy. Plants only turn between a fraction of a percent and a couple percent of the sunlight that hits them into food calories. Growing, harvesting, transporting, and processing food often consumes more energy than the plants contain in food calories. Especially if you eat meat. As much energy goes into producing a kilogram of beef (that's ~2600 calories -- roughly 2 hours of fast biking (35-40 miles) or 4-5 hours of moderate pace biking (~50-60 miles)) as your average European car consumes in 155 miles. And the numbers are only this close because the cyclist is moving so slowly.
Cyclists never like to hear this, but it's an unfortunate reality. Vegan cyclists are generally being fairly environmentally friendly by riding instead of driving, although the numbers aren't spectacular. Cyclists who eat a lot of meat distinctly are not.
Snowdog 5:02PM (9/19/2008)
meme. I think you will find that the "study" suggesting that driving was more environmentally friendly than cycling/walking was of the same caliber as the one stating Hummers were more environmentally friendly than a Prius.