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Diesel vs. Hybrid

Many folks who are pretty clearly disingenuously rooting for hybrid automobiles to go away because they don't like their implications for US automakers like to harp on the supposed superiority of diesel cars. Coincidentally, I just got an issue of Consumer Reports in the mail where the new Jetta TDI goes up against the new Civic Hybrid. Some stats from the article:

CarCityHwy0-60 time
Jetta TDI24 mpg46 mpg12.2 seconds
Civic Hybrid26 mpg47 mpg11.7 seconds
Prius35 mpg50 mpg11.3 seconds

And of course, the Civic Hybrid pollutes a hell of a lot less than does the Jetta, even with the forthcoming cleaner diesel fuel. The Prius is the cleanest of the lot and considerably larger than the Civic or Jetta. (I don't remember the 0-60 time for the Prius).

So, folks, the next time somebody tells you that hybrids are a joke compared to diesels, be aware they're selling you a load of bunk. Even in highway driving where diesels were supposed to be better, it turns out hybrids are winning in the real world.

(acceleration figures are from the magazine for Jetta and Civic Hybrid; attempted to get CR's figure for Prius via google, but may be unreliable; other sites have its 0-60 all over the map from sub-10 seconds to more like 12).

This entry was posted in the following categories: I Told You So , Transportation


Where are the figures for the Golf TDI? And you might take a look at the USA Today road test. Result: "Jetta lived up to its one-tank billing. Prius did not."


I've driven them all; I bought the Golf. I have a friend who races Enduro - he's buying a Golf TDI for it. I have a co-worker who drives a Prius; we get the same mileage, but I drive at least 20 mph faster than he does on average. My wife has a friend who races and currently drives a WRX; she's trading it in for a TDI after one test drive.

I wouldn't say that hybrids are a joke, but so far they have felt like the engineers who designed them definitely road the train to work.

The Prius has a 10.9 gallon fuel tank, quite a bit smaller than the Jetta's fuel tank. Simply having a magazine state that "the Jetta lived up to it's one-tank claim while the Prius did not" is about normal for current media. It is a total nonsense.

I've obtained an easy 51 mpg average on my Prius, which will give me a 550 mile range if I chanced it. I've tried doing it once - and put in 10.7 gallons - that was cutting it WAY too close - so I won't do that again!


The article didn't test the Golf. Probably because it's even smaller, and hence not a direct competitor to the Civic et al? I dunno.

Obviously mileage ain't everything or most Prius drivers would be driving Insights. But for a midsize car to beat all of these compact cars in fuel economy is a real achievement - one that should be celebrated, not downplayed.


I have a friend who still works at IBM in Austin (commutes in daily from Round Rock) and has averaged 56 on a tank. (I think his typical average is now around 54).

We don't do anywhere near as well - way too many 1 mile trips on cold engine to the grocery store, not many 30-minute drives. Where the EPA's test really screwed up was city driving - the assumption that most city trips were 30 minute traipses through the city doesn't hold up for anybody I know. The highway mileage, on the other hand, was spot on.

And on the rare occasions when we DO drive in the city for 30 minutes, we do, in fact, hit around 60.

The Golf interior is as large as the Jetta (same "frame"), i.e. about the same size as a Civic.

I've gotten to 810 miles on a tank, but I had to go 60 mph the whole time (and those last few miles were harrowing because I didn't know where it would end).


The CR article tested the Jetta because it's brand new. Presumably a Golf will eventually come out on the same platform if your comments are correct? Nevertheless, given how large a gap existed in CR's testing between the Jetta TDI and the Prius, it's doubtful an updated Golf would come close.

What we seem to have here is a case where the diesel drivers who are getting the BEST mileage possible on their platform are treating their mileage as 'real-world' against the LOWEST mileage estimates for the corresponding hybrid competitors. Apples to oranges, in other words.

When I searched on "Golf Prius", the only applicable sites I found in the first page or so were (a) comments about the greater CO2 emissions from the Golf (which has to be from fuel economy) and (b) FUD from the diesel guys about how you have to replace Prius batteries frequently.

If you look a little closer at the USA Today article, it states that the Prius' display said it got 51.7 MPG, which is substantially better than the Jetta's 44 MPG. The writer probably didn't know about the Prius' flexible fuel bladder and took the calculated MPG of 38 to be the more accurate number.

Anyone who owns a Prius knows that the flexible fuel bladder causes the tank to have an inconsistent volume, so you can't measure fuel economy by using the volume of a fill up. I've tracked my own fuel economy, and the hand-computed MPG tends to fluctuate around the displayed MPG, indicating that the displayed MPG is the more accurate number. I just find it unlucky that the hand-computed MPG happened to be inaccurate on the low side rather than the high side.

Incidentally, I consistently get 51 to 54 MPG on the highway, so the displayed MPG of 51.7 in the article is about right.

Hybrids are limited and now are only used with gas engines. Put a hybrid electric motor with a diesel engine and see 70 mpg. This is far less limiting plus the advantage of using biofuel will make our consumption of crude oil decrease dramatically. This is the way to go until fuel cells and hydrogen come to fruitation.

Unlikely. Diesel-electric hybrids haven't been very successful so far even as prototypes except in very very large vehicles. From what I read, too many of the advantages of each overlap - meaning you carry the extra weight / pay the extra cost twice for the same benefit.

Biofuel only helps if the EROEI is well above 1.0. No commercial production comes close today.


There are a great number of prototypes already gettting between 70 and 115 mpg using hybrid electric joined with a diesel motor. Besides, diesels can be run with used agricultural oils (low cost, environmentally friendly). Subaru, Peugot, VW, Mercedes, Ford and Chrysler already have working prototypes. The Ford Reflex may be in production by 2009 getting 65 mpg while also accelerating at under 7 seconds 0-60, and looks very sporty. Hydrogen cells and ethanol are also moving into production in the next 5 years. Diesel hybrids offer more benefits than any gas hybrid ever could and is definitely a move in the right direction.


If we're comparing prototypes, Toyota's 3rd-gen Prius is rumored to be shooting for >100 mpg. I prefer to compare what we can see today - the 2nd gen Prius is making Toyota a profit at 55 mpg; and no diesel of similar size can come remotely close.

The average mpg from Prius drivers is only 44 mpg not 55. In Europe, the Lupo and Polo both exceed the Prius mpg as does the Honda Insight. The 3rd generation Prius will not make 100 mpg because it is a gasser. Diesel engines achieve at least 25% greater fuel efficiency. Diesel will always beat a gasser of the same size and vehicle weight. My VW gets 45 mpg without any special driving techniques mandated by hybrid gassers. I hate to tell you this, but diesel powered vehicles will more than quadriple in the next 4 years. The Prius will either convert to diesel (yes, Toyota has two diesels already for sale outside the United States) or be left behind when newer vehicles will achieve 70 mpg and up. VW has one car ready for production hybrid diesel capable of 118 mpg, though the strict emissions requirements in the U.S. are holding it up. With the introduction of ultra-low sulfur diesel, more biodiesel pumps becoming available daily, and the use of agricultural oils as fuel; diesels will have no trouble becoming as popular in the U.S. as they are in Europe (where nearly 50% of all vehicles sold there are diesel). Watch the gas prices go up, and with it diesel sales too. Nice positive correlation between the two. Thanks Bush for this wonderful economy.

That's apples and oranges - again, you're comparing midsize hybrid Prius to small diesel (or to diesels with comparably little power, or both; the US VW's are smaller AND slower).

And yes, the Prius gets 44 when driven naively - but it still beat VW's US diesels in the same exact test when driven the same exact way in both city AND highway mileage. So it's difficult to see this incredible technological advantage you assert. If you're getting 45 in your diesel, you'd probably be getting a lot more in the Prius, since you're overachieving compared to what CR was able to do.

Again, Toyota supposedly has a 3rd-gen Prius on the way at 100 mpg. If you can use prototypes, so can I. Otherwise, we're limited to head-to-head comparisons, and so far, the Prius has kicked every diesel competitor to the curb (even the smaller ones).

Curb weight, Toyota Prius = 2921 lbs.
Volkswagen Jetta = 3352

Sounds like you got it backwards as far as size goes. The Jetta gets 45 mpg without an electric hybrid motor added. Add hybrid technology to a diesel and see that 45 mpg change to 57 mpg. I advise you to read up on diesel fuel efficiency compared with gassers. The Prius has not beat diesels in mpg comparisons. I get 700 miles per tankful, what does that Prius of yours get? If you think I am making this up, please visit tdiclub.com and see how some people there achieve 800-1000 miles per tankful with their Golf and Jetta. http://www.usatoday.com/money/autos/2004-06-10-diesel-vs-hybrid_x.htm
Best price Toyota Prius from Carsdirect.com = $25,559 compared with best price for a VW Jetta = $22,235. Oops beat the Prius again. Now, let's go to the pump. Regular unleaded at $3.09 per gallon while diesel is at $2.85. Oops Prius beat again. Prius is a bandaid and still relies on foreign oil. Diesel run on Wesson oil, used McDonald's grease, biodiesel mixture, or diesel fuel at the pump, less reliance on foreign oil to no reliance on foreign oil. Along with diesel engines, hydrogen fuel cells, and ethanol have a chance to take the place of regular gassers. Sorry, but the Prius' days are numbered while my diesel's future is expanding to markets all over the world. Have you driven a diesel lately?


Try 60 mpg not 100 mpg if they build the 3rd generation exactly like the prototype.

If we get the 75% of claimed fuel economy like we have been getting from recent hybrids, then the next generation real world fuel economy will be 48 mpg-no where near your claim of 100 mpg. I think you need to join me over in the diesel camp.

If Toyota is smart, they will add a plug in variant to the Prius line up and use lithium battery packs for longer life and less weight. These two add ons could yeild very positive fuel efficiency gains.

I apologize. I found a blog reporting 113mpg for a prototype Prius with lithium batteries (though it used British gallons which are larger than ours, but still would equate to roughly 94mpg U.S.) with plug in variant a possibility too. So, yes, they will push the envelope for gassers and could garner an $8000 tax credit if they achieve their goal. So, Prius is not yet done it looks promising.

So, now we add this technology to a diesel and see roughly 125-130 mpg U.S. How does that sound?


Read the beginning of this article - you know, the one that you've been commenting to all this time. The Prius beat the Jetta TDI head-to-head in both city and highway driving when both were driven by the same (probably typically lead-footed) driver at CR. Comparing "best" mileage from an enthusiast site for diesels against the "worst" mileage from CR for hybrids is exactly the kind of apples-and-oranges anti-hybrid FUD that I was writing about to begin with. If you can pick diesel-enthusiast mileage, then we're back up to 60 mpg for the Prius.

As for size - the Prius is classified by the EPA as a midsized (family) car. The fact that the Jetta _weighs_ so much is amazing considering it's not very big. The EPA classifies the Jetta as a small car.


And around these parts, diesel is usually more expensive than regular.

What, exactly, is your agenda here? Every single thing you post is pretty easily disproven.

Plus to equal the equipment on the Jetta, the Prius buyer would have to pay extra for electric seats, stability control, additional air bags, security system, mp3 player, and 12 months more warranty. I would say the Jetta is looking pretty good to me.

The interior and exterior dimensions are nearly identical between the two cars. The weight difference makes the Jetta feel more substantial and safe. In fact, it outscored the Prius in government crash tests. For thousands less, I choose the Jetta. Why are you ignoring the article from USA Today? CR reports gas test is not real world. It combines three very short drives totally 150 miles.


The USA Today article is fatally flawed - measuring a "tank" without talking about how many gallons were in there, and without mentioning that the Prius, for reasons of emissions, has a variably-sized fuel tank which makes readings "at the pump" notoriously unreliable.

Why are you resuscitating this FUD?

The Prius is a midsize car by EPA standards; the Jetta is not. Period.

The Jetta is listed at 107 cu. ft. total interior volume and the Prius is at 112 cu. ft. interior volume including the hatchback. I doubt anyone would feel it is a smaller car. Have you driven both? I have and I made my choice accordingly. It is important for all of us to look at all the data available. The bottom line is that diesel compete very well against hybrids. My point is add hybrid technology to diesel cars/trucks and we will get an even better product on the road which is what I hope we both want. USA Today is as flawed a mileage study as CR. It appears that CR is not the gospel it is made out to be. I can offer you many statistical errors CR makes if you would like me to get into that discussion, then let me know.


CR's test is fair - even though they rate the Prius far lower than what we get, because we try to get good mileage (they don't). The difference between that test and what USA Today did is that USA Today made a measurement error (the flexible fuel bladder makes it unreliable to measure fuel consumption at the pump).

And, frankly, diesel hybrid doesn't make much sense to me. Too much overlapping efficiency to justify the added cost.

One thing about diesel fuel, it foams. You can never get an accurate pump measurement unless you vent it. By this, you let the tank exhale (relieve itself of foam) and get the exact same fill each time. If I just stop pumping diesel when the pump first kicks off, I am about 2 gallons short of full. I would venture to guess that CR and many other publications do not vent when filling a diesel. Two gallons is almost 100 miles more per tank. Anyway, back to my suggestion of a diesel hybrid. Diesels run about $1000 to $1500 over the price of a comparable gasser. Add another $3000 to $5000 for hybrid technology. Example, Gas Jetta costs around $22,000. Diesel Jetta around $23,000. If there were a hybrid offered as well, it should be in the neighborhood of $26-$29000. This is a reasonably priced automobile especially since it would be getting about 70 mpg. This could save some people who are still driving cars getting 20 mpg a lot of money. I think it will be well worth it.

CR does not fill the fuel tank up. Diesel fuel foams and needs to be vented in order to fill it up to the top and consistently. Check out the April 24th AutoWeek, Jetta got 49.9mpg and the Prius got 42mpg. Also, diesels do not need to be driven gingerly to accomplish top fuel returns while hybrid gassers do. Diesels are outperforming hybrids without having the added hybrid technology. Like I said before, add the hybrid technology to it and the gasser hybrids are left even further back.

The AutoWeek test is such an outlier that it would seem more likely that they somehow screwed up the hybrid measurement - for instance, repeating the USA Today error of measuring fuel at the tank instead of trusting the readout.

If diesels have such a hard time with adequate measurement, it would seem logical to have the same kind of readout for confirmation of fuel economy.

Frankly, I have to wonder about your objectivity here, though, with the continual references to "gassers" and the like. The fact is that the Prius is beating the Jetta in every highway test in which the car's computer is read - and you keep reaching for future prototypes to bolster diesel's case while refusing to do so for hybrid. All while ignoring the fact that the Prius is the next size class up from the Jetta.


So, is the latest issue of road and track an outlier as well? They finished a **two year** test on their prius, and it got 41 mpg. seems like a pretty accurate example of what one could expect in the "real world", wouldn't you say?

Your last comment about objectivity literally made me laugh, as it just oozed of throwing stones in a glass house. Both cars have their advantages, but you won't concede any where the Jetta is concerned, like long distance highway travel - an area where the prius cannot use it's regen feature.

At the end of the day, I chose the jetta and got more car for the money, better crash results, better highway mileage, and a car I won't be scared of owning in ten years.

I do wish a wagon was available, and salute the utilty of the hatchbatch on the prius. something the latest gen Jetta TDI does not yet offer.


Haven't seen it yet, but yes, that would qualify, and if they drove the Jetta for that long, it'd finally be an apples-to-apples comparison along the lines of CR's test in which the Prius just destroyed the Jetta in the city, and beat it even on the highway.

Do you have R&T's 2-year results for the Jetta?

I can easily believe that at higher cruising speeds, the Prius' highway advantage over the Jetta diminishes or even eventually reverses, by the way, but you still then need to deal with the fact that the Prius is a midsize car, and the Jetta just a compact.

So, now do you believe me that diesels do quite well? Have you looked up any other articles? I read this cool article about using unpumped air in the engine as its own source of energy as well as another technology that converts heat from the exhaust into usable energy. Both these technologies together could increase fuel mileage by 25%. Not bad. Looks like the internal combustion engine has life still. The only viable competitor I see is the hydrogen cell which still seems years away.


Still waiting for an explanation of the Prius' outlier performance. Most likely one so far is that they repeated the USA Today error of measuring at the pump (unreliable due to the fuel tank bladder).

AutoWeek's story is now online, and as I predicted, they apparently measured at the fuel pump rather than trusting the on-screen display:


I doubt speed was as much of a problem as the measurement issue - I drove the Prius down/back to Port Aransas a few weeks ago and averaged 49, despite driving 70-75 mph most of the time.

Further adding to the point that when measured properly, the Prius kicks the diesel to the curb:



For your reading pleasure when you have a little time.


I went through and read the entire comment thread on one of those links before giving up in amazement - it's the same old FUD over and over and over again. "you'll have to buy a new battery!" (No, you won't). "it gets worse mileage than the Jetta!" (No, it doesn't). Etc.


Apart from the outliers which apparently measured fuel consumption at the pump (reasonable to do for most cars, just not the Prius), EVERY SINGLE TEST HAS SHOWN THE PRIUS BEATING THE JETTA, EVEN ON THE HIGHWAY.

This is the end of this thread.