Autoblog

All hype? Spoken like someone who hasn't owned one.

This test is proof that you can alter the conditions of any situation to get the outcome you desire. So a diesel gets good mileage on the highway. No surprise there. Too bad there are so few diesel cars in the U.S. and the fuel's outrageous.

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OK I am not a Prius fan but this comparison just doesn't seem right.

First, BMW is much more expensive.

Second, why did they only add 100 miles urban driving? Just felt pity for Toyota? If 460 miles were driven on BMW's strong point, then at least 350 miles should have been driven on Toyota's strong point (urban).

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I wouldn't exactly call the 520d "fast", but you're on the right track.

Diesels can give you better mileage without making you feel like you're sacrificing your driving experience in some world-saving crusade.

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Ultra Low Sulfer Diesel fuel should, theoretically, cost about 5% more than gasoline to produce from the same crude. The cost differences are due to a number of things including taxes, demand, and refinery capacity. Diesel contains about 10% more energy by volume than gas and therefore produces about 10% more CO2 by volume when burned.

If you're comparing diesel vs gas hybrids, you need to take into account the additional energy-per-liter/gallon, and you need to look at CO2 emissions.

The fact that the Prius had significantly better CO2 emissions is an important stat.

The end result is: they're both great cars, they have different advantages, and they serve different purposes.

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For many it will be to spend $60,000 or $24,000. Also, lets factor in the additional cost of diesel fuel which I understand is currently running upwards of $1.00 more per gallon.

I would love to have a BMW diesel, don't get me wrong, but the Prius still has that crown as an affordable "green" car that gets good gas mileage with midsized car room and hatchback versitility.

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@Duncan:

"Diesel contains about 10% more energy by volume than gas and therefore produces about 10% more CO2 by volume when burned."

Just to clarify: diesel contains more energy because it weighs more. It weighs more because it physically takes more crude oil to make a gallon of diesel than a gallon of gasoline: depending on estimates, it's between 15-25% more crude per gallon.

Then there's the high-strength block, high-pressure injectors, turbocharger and emissions control system. Granted, not quite as complex as a parallel hybrid, but not as simple as a naturally-aspirated gas engine, either.

Compression ignition is a good technology, but I think there's a bias amongst gearheards towards diesel, and it's one that conveniently glosses over the true fuel requirements and complexity inherent in a modern TDI.

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@psarhjinian Right, it's 15% not 10%. Diesel is also easier to produce than gasoline, so it's not quite 15% more expensive to produce. Like I mentioned, the price difference in the US is do more to demand/refinery capacity (supply) than being more difficult or expensive to manufacture than gasoline. Remember that recently diesel was cheaper than gasoline. The move to ULSD brought the price up slightly, as has demand.

While diesel engines are more expensive to manufacture for the reasons you mention, hybrids of course also add complexity. In addition, the diesel, properly maintained, should provide a more consistent level of performance over it's lifecycle than will a battery-assisted gasoline engine (which won't be reaching the same mileage numbers after 100k-200k miles).

There's tradeoffs for both. And this is really an apple-oranges comparison since the 5 series isn't really in the same size or price class as the Prius. I don't think many people are going to be cross shopping a $45k+ mid-sized sedan against a $24k compact.

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Addressing the but a Prius is smaller can cheaper. Over in euroland where this test was done BMW sell the 1 series as a 5 door hatch, one particular option is the 118d which retails for £18,800 as whilst a basic Prius T3 is £17,777. So approx £1,000 more for the BMW. Both cars are in the same size class yet the official fuel consumption figures are:
Prius 65mpg (imperial), 109g/km
118d 62mpg (imperial), 119g/km

I'd bet that under a real world test the 118d would substantially beat a Prius. The offical figures for a 520d are:
55.4mpg (imperial), 136g/km

It must be noted that the co2/km figure is calculated from the combined cycle fuel economy figure so any test that over states economy will understate co2 emissions.

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Time for you to read the article. It even stated that the condition is unfair. Prius is an urban commuter..-- wait you probably won't read this anyway. Maybe you'll read nonsense: Blah blah you should read blah blah read blah blah tool.

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How do you think a diesel hybrid Prius would do?

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Except, diesel prices were kept artificially high. Diesel is cheaper to produce than gasoline, hence diesel at the pump should be cheaper, as it is everywhere in the world. In N.America you pay that premium to make someone else meet their quarterly results.

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MeToo: It's my understanding (and I'm definitely *NOT* a petroleum engineer) that while diesel fuel requires less refining than gasoline, with the methods used at US refineries you also get less diesel from a barrel of oil (because of the fraction of the contents of the oil that are suitable for producing diesel) so that tends to balance it some. The other part of the diesel price in the US is that there are more refining resources dedicated to making gasoline (because there are so many more gasoline-burning vehicles here) so as demand goes up there's just less diesel inventory, driving the price up a bit faster.

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The reason you get less Diesel than gas from a barrel of oil is because the Diesel contains 15% more energy per gallon. It has 15% more H-C-Hs per gallon, and a barrel of oil only has a fixed number of these. If you put 15% more of them in a gallon of fuel, you're going to get 13% fewer gallons fuel out.

It's not a US thing, it's a chemistry thing and no magic is going to change it.

Note that if didn't crack or polymerize any H-C-Hs that you get from oil, you would indeed get more Diesel from a barrel of oil than you do gas. But those days are a long way behind us now. Modern Diesel isn't just bunker fuel anymore. As Diesel emissions standards have become tighter, the requirements for the fuel itself have become tighter, and now Diesel requires a lot of reprocessing, just as gasoline does.

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not so fast there LS2/LS7.... It ACTUALLY IS a US thing....and yes chemistry does have a role in it. More specifically the way you refine crude.

For explanation, here is a portion of Csaba Csere's article from Car and Driver, April 2008;

"AI Mannato, a fuel-issues manager at API, explains that oil refineries tend to fall into two categories: catalytic cracking and hydrocracking. Most U.S. refineries are set up for catalytic cracking, which turns each barrel of crude oil into about 50-percent gasoline, 15-percent diesel, and the remainder into jet fuel, home heating oil, heavy fuel oil, liquefied petroleum gas, asphalt, and various other products. In Europe and most of the rest of the world, refineries use a hydrocracking process, which produces more like 25-percent gasoline and 25-percent diesel from that barrel of oil. So the rest of the world is already maximizing diesel production. In fact, despite using a refining strategy that minimizes the production of gasoline, Europe still ends up with too much of the stuff, so it exports it to America-about one of every eight gallons of gasoline that we consume.

Meanwhile, Americans are already using most of the diesel fuel
that our refineries produce, so if sales of diesel cars take off, keeping the diesel flowing here will put further demands on tight worldwide diesel supplies and probably cause the price to rise even more. "

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No Frick.

Cracking and polymerization is what you are talking about, and I already addressed it. With some additional reprocessing you can break apart the molecules in the oil and make other ones from it. If you want more kerosene (jet fuel), you can get it.

But you also end up with less of something else. There's no free lunch. No part of a barrel of oil is wasted in the US or in Europe, so if you start looking for more of one thing, you give up something else.

And again none of this makes up for the fact that Diesel contains more H-C-H chains in it, and so you have to use up 15% more of the H-C-Hs from oil to make a gallon of Diesel instead of gas.

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Yes LS.

Read my post again. Try to understand it. Get back to me in the morning.

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The BMW "beat" the Prius by 1.8 MPG, but Diesel here in San Francisco is $4.20/gallon right now. The math is *not* working in its favor for just 1.8 MPH *highway* miles.

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