What place diesels?

Great Debates
1

In the current electric car thread Magiver posits that:

This op is to give that proposition a fair hearing in its own thread, comparing diesel to gasoline powered vehicles.

Under the current supply/demand conditions diesel cost more than does gasoline in America. Currently it runs about $0.28 more per gallon. The highest the national average for gas, during the 2008 spike, was $4.114. Diesel that week was $4.845.

And that’s at current demand. Gasoline is cheaper than diesel for several reasons, costs of refining among them (it costs 10% more per gallon to refine it), but more than any other reason because of supply and demand: the EU has historically taxed petrol much higher than it taxes diesel, making diesel 10% less at the pump than petrol despite its true cost beng higher, hence more diesel vehicles, hence an excess of gasoline to come here, lowering the price of gasoline relative to diesel. Gasoline and diesel are both produced from the same barrel of oil with the gasoline fractionating at lower temperatures than diesel. Diesel then has more refining to make it ready for use as a fuel. More global demand for diesel relative to demand of gasoline would markedly increase that price differential. Which would increase the goods of products shipped by trucking.

Nevertheless diesel is more efficiently used. Some sites claim 30 to 35% more efficient, some 50%. The difference of course will vary with the particular models. Be careful to compare imperial gallon to imperial gallon and to use the same test cycle, not comparing to EU cycle to the EPA one. So for example, the Ford Fiesta diesel ECOnetic gets 76.3 mpg on the EU cycles compared to the comparable petrol Fiesta which gets 51.5.

Diesels cost more than do gasoline powered vehicles. For example the Ford Fiesta ECOnetic costs 13.895 pounds compared to 10,845 for the comparable petrol model. In dollars that’s a difference of $4964, almost 30% more.

So 12,000 miles in a year on average. The diesel will need 157 imperial gallons which is 189 US gallons at a cost today of $779 for the year. The UK petrol model will need 280 US gallons at a cost of $1157. That’s a savings of $378/year. It would take over 13 years to have a return on investment. Add on more to bring the UK diesel model into compliance with American standards. (For some reason the EU cares less about the effects of diesel particulates.)

At the current (and fairly consistent as a floor) U.S. price gas/diesel differential a diesel getting 50% better fuel economy that its comparable gas model would pay for itself over the usual 5 years of ownership only at a premium of $1890 or below, not the almost $5000 premium that actually exists.

In America, where no preferential tax treatment exists for diesel fuel, diesel cars are currently not any sort of solution.

2

Oops. Caught a math error. I multiplied the petrol model by the diesel cost per gallon. It’s actually $1080 per year for the gas and the difference in fuel costs is only $302/year, which makes the ROI actually over 16 years. My apologies.

3

Diesel engines last a lot longer too. In Dearborn diesel fuel is more expensive ,so that cuts savings back a bit.

4

But modern gasoline engines last essentially forever if properly maintained and not abused. They certainly last much longer than the cars they’re put in. The inherent longevity advantage of diesels would only come in to play many hundreds of thousands of miles down the road, when most cars have been junked. The very long-term survivability of a car is of no interest to most new car buyers.

I would like to see more diesel cars in this country, but just like (current) hybrids, they’re niche vehicles for the very few drivers who drive enough to reach the break-even point in a timely fashion. One thing people forget is that the European super-mileage diesels are also niche products-- they are cars that are built for people whose main concern in a car is fuel economy. They are often very slow and poorly-apportioned compared to their gasoline ilk, so it’s very rarely an apples-to-apples comparison. For example, in the Fiesta comparison, there is a “regular” diesel option that’s much closer to the petrol engine in performance and mileage. The ECOnetic Fiesta is a fuel-sipper option package with no gasoline equivalent. In other words, you could also get much higher mileage gasoline vehicles if buyers were willing to put up with the poorer performance.

And the actual practical advantage diesels provide is often over reported. They are much more efficient theoretically in that less of the energy in the fuel gets converted to heat, but that doesn’t translate directly into better fuel efficiency. The real-world fuel economy advantage over a comparable gasoline engine is usually about 20%. That’s good, but not good enough to base an energy policy on, especially when there’s the economic perils of using a fuel that’s used for so much else. It might make more sense if a workable biodiesel scheme existed, but at the moment there isn’t one, nor is there one that looks particularly promising in the near-term.

5

I’m sorry, but a 20% improvement in fuel economy (my Jetta TDI seems to get about 30% better mileage than a standard one, BTW) is a massive game changer in terms of energy consumption.

Let’s also keep in mind that part of the issue with the cost of diesel and engines is the currently complex supply chain. Diesel engines make up a small fraction of current automotive production, so of course they are more expensive. Given economies of scale on the same basis as today’s gasoline engines, is there any reason why diesel engines wouldn’t cost thousands less than they do today?

6

In some European countries up to 70% of the new car market is comprised of Diesels - so to talk about volume is a somewhat USA Centric argument.

7

Firstly, yes, there are fundamental manufacturing issues that make diesels more expensive. Diesels aren’t Wankels-- they are a technology that is just as fully developed as a gasoline engine. Even though diesels make up a somewhat smaller portion of car engines world-wide, there are some diesel engines that are produced in huge numbers which are still more expensive than gasoline equivalents.

My take on it is that what makes diesel different from electric and hydrogen technology is that diesel is a dead end. With electric or hydrogen, it makes sense to subsidize them because they are developing technologies and making them artificially economically viable helps develop those technologies to a point that they will no longer need subsidies. Diesel has had roughly the same efficiency advantage forever, so the government would have to subsidize diesel indefinitely. I personally do not believe that a 20% improvement in passenger car efficiency is enough to justify the ongoing cost it would incur, especially given the potential economic problems.

8

Locomotives have been diesel-electric hybrids for half a century, at least. What kind of mileage and performance could a Prius-size diesel hybrid get?

9

Would it be relevant to ask,

If I could wave a wand and transform the entire US passenger car fleet to diesel overnight, what impact would that make on meeting the desired obligations under Kyoto.

I know that if you could do the same with the Singapore private car fleet, you would meet the govts stated targets on emissions reduction.

10

That’s not quite the same because diesel electric locomotives don’t store any electricity. They basically just use the generator-traction motor set up as a transmission. Interestingly, the dynamic brake on a diesel locomotive functions the same as the regenerative brakes on a Prius in that they use the traction motors as generators. But the locomotives can’t store the electricity, so the load is provided by heating elements that serve no other purpose.

Diesel hybrid cars might work, but they would not resemble the current gasoline-hybrids. I think one problem is that there’s overlap in the advantages of hybrids and diesel-- diesel’s better low end torque and more efficient idling would be moot in a hybrid. The real potential would be in having a really small diesel (like maybe a 1-cylinder) that wouldn’t by itself provide acceptable acceleration but could produce gobs of torque in it’s narrow torque band to turn a generator. The resulting car would have to have somewhat limited performance and might even run out of power from time to time, but it could be incredibly efficient. The trouble here is that you would be looking at a fairly expensive car (paying both a hybrid and a diesel premium) that performed relatively poorly. The poor market for diesels in general in this country shows that new car buyers are not interested in making that compromise. If fuel gets much more expensive, maybe that will change.

11

Maybe the situation is different in Singapore, but in the US, cars and light trucks only account for about 22% of carbon emissions. If you made those 20% more efficient, you’re looking at a 4.5% reduction in emissions. That’s definitely not nothing (that’s about Argentina’s carbon output), but IMHO you could do better with the amount of money and ongoing effort that would be required to actually switch most cars over to diesel.

12

The big question though would be - how much spending is required?

As of today, switching to diesel wouldn’t require a subsidy, special infrastructure or anything else.

Simply reduce the fuel tax and there you have it. Diesel would be a natural winner in that sort of circumstance.

Not least of which, Diesels are starting to make quite serious inroads into performance car sectors…

13

How do you figure that math?

14

Well I assume you do have excise tax on fuel right?

Less tax = lower price = consumer incentive to change :smiley:

I’m not speaking greek am I?

:dubious:

15

Remove the tax on fuel. Diesel is still $0.15/gallon higher than gasoline on average and the cars are still that much more expensive to buy. They are still the same get the same 30 to 50% better mpg. The ROI on the price difference between a diesel car and its gasoline counterpart in that case is about 14 to 15 years.

No you are not speaking geek. You also are not speaking any sort of sense.

16

The ECOnetic is the most expensive diesel Fiesta, and the petrol model you selected as “comparable” is almost the cheapest petrol model.

Nice try.

17

Diesels still have a massive image problem in the U.S. I know, all those problems (they’re noisy, they smell, they run badly in cold weather, etc.) have more or less been solved, but there are many posters on this board who still speak quite disparagingly of automatic transmissions, even though those concerns have largely been eliminated, as well.

I see a lot more acceptance of diesels in rural areas where a) people have more experience with the engines, because so many of their trucks have diesel engines and b) every gas station also sells diesel.

18

They have the same problem in the UK and Europe.

The difference is that the fuel tax encourages diesel ownership there since (1) diesel is taxed at a lower rate, and (2) all fuels are taxed at a much higher rate relative to the US, meaning fuel economy is a much bigger selling point.

19

Even if you completely eliminated the fuel tax, diesel still isn’t cheap enough. Out here they sell non-taxed off-road diesel and it’s still more expensive than gasoline at the moment. Even with the fuels on par, it still takes a long time to pay off the diesel premium. And suddenly forgoing a huge portion of the fuel tax would still be quite expensive for governments. Plus as others have pointed out, suddenly shifting a huge portion of the passenger car fleet to diesel is certain to cause that price difference to widen, requiring more government meddling to keep it economic. One of the biggest economic advantages of gasoline is that it isn’t used for anything else but powering small vehicles. Diesel, on the other hand, is used in everything from tractors to supertankers as well as for home heating and power generation. If you want diesel to power your cars too, you’re going to need to find ways to make a lot more of it and/or risk some serious price fluctuations in all of its applications.

As for the government subsidizing the cars instead, they’d have to pay for all or most of the diesel premium which, in the case of the Jetta and Golf, is about $5k. With about 8 million cars sold per year (we’ll say 7 since some will still be gasoline cars and some are already diesel), that’s 35 billion with a b per year. And, to make the majority of the fleet diesel, you’d have to keep at it for somewhere in the 5-10 year range (at the present about 38% of cars in the US are older than 10 years old). That might seem not insanely expensive compared to other carbon reduction schemes, but it’s not an investment-- if the government halted subsidies people would eventually go back to gas cars (especially since gas would be increasingly cheap).

Like I said earlier, if you had a way to produce more diesel, like a workable biodiesel scheme, diesel cars might represent more of a way forward, but even then only if biodiesel could compete with gasoline on price (be it due to cheap biodiesel or expensive gasoline).

20

It can’t be quite as bad in Europe-- they never had to endure the supremely awful Oldsmobile diesels.