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Study: Diesel May Outpace Gasoline Hybrids in US

The relative merits of gasoline hybrids and diesels.  Click to enlarge. Source: Ricardo estimate, Schommers, DaimlerChrysler, GM, Aachen, October 2005

Although hybrid gasoline technology currently appears to be the preferred route to increased fuel efficiency in the US, new investment research published by UBS and Ricardo predicts that sales of diesels will outpace those of hybrids by 2012.

Diesels will constitute 56% (1.5 million units) of a forecasted combined diesel and hybrid gasoline sales of 2.7 million units in 2012, according to the study. At 2.7 million units, the two technologies would represent 15% of the US light duty vehicle market. UBS highlights that European automakers and a number of global suppliers look set to benefit from the diesel trend.

Cost comparison of gasoline, diesel and hybrid for a 4-liter V8 powertrain in the US. Cost gap for smaller cars is closer, but still favours diesel. Click to enlarge. Source: Ricardo

Prospects for both technologies are strong, according to the report, given the increasing regulatory focus on fuel economy and reduction of greenhouse gas reductions. However, it concludes,  diesel’s cost burden is lower than that of hybrids for similar fuel economy, even with the advanced technologies needed to meet tough US emissions regulations (including California).

Diesel’s cost lead over hybrid is the most marked for larger vehicles (crossovers/SUVs).

Should the energy storage cost barrier be overcome, the report notes, plug-in hybrid vehicles have longer-term future opportunities.




Is there something wrong with deisel hybrids? Do deisels not idle at stop lights? Would they not benefit from regenerative braking? These are not competitive solutions. They are two different choices for future efficiency gains that can be complimentary.
For that matter, hybrid technology makes sense for ethanol too.
I see no reason why hybrids won't continue to gain marketshare even among deisels. Even deisel or ethanol gensets for PHEV's make sense.

C Harget

It's not a question of are-diesel-hybrids-better-than-just-diesel. The chart shows a Diesel hybrid would have the best of both worlds. The question is, "How much extra does hybrid add to diesel?" The answer varies depending on the driving (in the city, a lot), the vehicle class (heavier vehicles, full hybrid is harder), vs the added cost of full hybrid. Clean diesel seems worth looking at because it gets more miles per gallon than standard gas. But, doesn't it take more oil to refine a gallon of diesel than a gallon of standard grade gasoline? How do diesels compare from a well-to-wheels point of view? Also, is the clean-diesel tech clean enough?


That begs an interesting question, from a CO2 standpoint, which emits more CO2, a gallon of diesel or a gallon or gasoline?


Diesel and parallel gasoline hybrids are competitors. A TDI diesel uses no fuel while coasting to a stop and a TDI diesel uses almost no fuel while idleing (my golf uses only .6L per hour!). It is true that regenerative breaking could be implemented on diesels, but you could not gain much of an advantage from it because it wouldn't allow the engine to be downsized anymore (gasoline engines for any given application are sized significantly higher than their diesel counterparts). Electric assist on launch is not as useful on a diesel as on a gasoline vehicle because high torque at low RPMs is where diesels shine.
I submit that A 76HP diesel engine in a Toyota prius hybrid would net less than a 5 MPG gain over a standard Miller cycle Prius. This while increasing tailpipe emissions, increasing NVH, and adding a couple of thousand to the price tag.
I like hybrid tech and diesels (I own one of each), but in the parallel setup they are redundant.


Darwin, you're making too much sense.

But, doesn't it take more oil to refine a gallon of diesel than a gallon of standard grade gasoline?

No, just the opposite.

How do diesels compare from a well-to-wheels point of view?


Also, is the clean-diesel tech clean enough?

If it isn't, neither's gasoline, especially the way gasoline technology is going (stratified charge lean burn)


It is clear that a gallon of diesel emits more co2 than a gallon of gasoline. The relevant parameter is co2 per mile or co2 per km.

The other thing that should be kept in mind is that Toyota is briging the marginal cost of hybrid technology down to at least half of what it is now. In addition, some say that the next gen Prius, for example, will get in excess of 65 mpg. That could be a game changer.


Nothing on the table right now is a game changer. Everything on the table still play by the same rules, and it's by those rules that we need to figure out how to encourage people to drive more efficient vehicles.



Gallon of gasoline weights about 6 lb, gallon of diesel weights about 7.2 lb. Would be interesting to see how it takes less oil to produce gallon of diesel than gallon of gasoline.


It is also clear that a gallon of diesel contains more ENERGY than a gallon of petrol.

The other reason why you don't have diesel hybrids is cost. The fuel injection and aftertreatment systems of a modern diesel are not cheap (esp if it is to meet T2B5). As a result of this and the fact that a diesel is a better compromise than a petrol hybrid under most circumstances make a diesel hybrid less likely.

Stan Peterson

Diesels are a temporary improvement at best. ICE efficiencies can go up from 25-35% by use of the diesel cycle. But after that there is nothing further to be gained.

Diesel answers no long term questions. If the Peakists are eventually correct, diesels are not the answer. If the atmospheric concerned are eventually correct, Diesel is no long term solution there either.

Only ground transport electrification makes long term sense.

Thankfully this report fits into the category of 'Garbage IN, Garbage OUT'. The cost differential for the capital expenditure for a clean diesel is overlapped by the higher capital expenditure for a full hybrids. But this study does not account fro or include operating expense. There is mighty few gallons of diesel fuel available for 75 cents a gallon equivalent as the hybrid offers. So even in the short term clean diesel won't have much of a permanent economic advantage, if any.

If as seems probable that Toyota can indeed drive the manufacturing learning curve and the battery learning curve down to a mere $1000 capital difference between a hybrid and a conventional gasoline engine, there will be no capital difference between a diesel and a hybrid. Toyota aims ot achieve thsi is as short a period as two years.

In actuality, the diesel capital cost may prove higher.

Would you purchase the car than can be fueled for 75 cents a gallon or the same priced one, that must be fueled at $3-4 dollars per gallon?

Question asked; Question answered.


If a move to diesel slows or delays the implementation of PHEVs by reducing the adoption of HEVs then this is not good. While diesels are better than gasoline cars, there still remains to major problems. One: they still get all of their motive power from fossil fuels, mostly oil. Two: now we have even more direct competition between private, often unnecessarily driven, LDVs and the delivery trucks that brings our food to market.


Scott: The figures I've generally seen are 2.7kg/l for diesel and 2.3kg/l for unleaded gasoline.


During the 90's GM, Ford, and Chrysler independently arrived at similar conclusions to meet PNGV's family sedan challenge: light weight, diesel-electric hybrids.

Cost is the detractor:
If a clean turbodiesel adds $2,500 to the cost of a vehicle, and hybridization adds another $4,400- how many consumers are willing to fork over $7,000 in the name of fuel efficiency? (notice, I did not take into consideration the cost of lightening vehicles- a fuel saving measure that, to date, has not been expolited)

What does the $7,000 price premium buy the US consumer?
Take two identical vehicles: one with a conventional 30mpg drivetrain, the other with a 70mpg diesel-electric drivetrain. Driving both 15,000 miles per year, while paying $4/gallon for fuel:

70mpg diesel-hybrid requires: 214.3 gallons or $857/year
30mpg conventional drivetrain: 500 gallons or $2000/year

At $4/gallon it would take over 6 years of driving to recoup the $7,000 price premium for the diesel hybrid.

This is where tax breaks and subsidies would help. From a National Security perspective cars using 214 gallons/year are much more favorable than 500 gallons per year, let alone over 700 gallons a year (as present US fleet average fuel economy dictates).

Ralph Taite

To Stan Peterson: Take it a step further. We need electrification of ground transport AND the electrification of all highways. The second will save millions and millions of gallons of oil.


Andrey, I note you're using weight and not volume or energy. Anyway, if you fractionally distill a barrel of oil you'll get 5-20% diesel (depends on crude), which you test for cetane and maximum sulfur (again, depends on crude), and that's it. You will get no gasoline. To get gasoline you have to make it, which means combining the naphtha (which you do get) with fractions (some naphtha, some heavier) you isomerize and fractions you crack into small aromatics. Demand being what it is, you'll likely also crack heavier fractions into naphtha. Then you combine it all, check for octane and max sulfur content. The additional processing steps of cracking and reforming all take energy.

If a move to diesel slows or delays the implementation of PHEVs by reducing the adoption of HEVs then this is not good. -- Neil

Agree 100%. It's hard to see that ICEs will go away in the next couple of decades, so hopefully maturing technology will significantly lower the premium for diesel hybrids. Preferably serial, Volt style. And hopefully all urban traffic will be electrified.

Diesel answers no long term questions. If the Peakists are eventually correct, diesels are not the answer. If the atmospheric concerned are eventually correct, Diesel is no long term solution there either. -- Stan Peterson

Good Lord. I agree with Stan Peterson!


In the summer of 2005 we were in the market for a new car. We wanted a high mileage vehicle for our long commute to work. We drove both the Prius and the Jetta TDI. They were very close to equal in many ways; price,mileage,room. The Jetta felt like a better car, drove better, handled better. We run our 2005 TDI on bio and are very happy with it. I think this report realizes in a side-by-side comparison most people will see that the diesel is a better car, from an asthetic point of view.


bad news- according to the American Petroleum Institute, most of the refineries in this country are optimized to produce gasoline (despite as coal burner correctly points out, the fact that there is less gasoline available in a barrel of oil than diesel.) And, despite that optimization, we can't even provide enough gasoline to keep up with domestic demand. In fact, 1 in 8 gallons of gasoline in this country is imported from European refiners.

If the refiners wanted to switch to optimize for diesel, it would require an investment in the ball park of $500MM-$1bb PER refinery, along with a 4-5 year lead time.

The point is, until that potential switch, diesel supplies (which are already tight globally) would be increasingly strained, driving up prices above gasoline (which they already are in the US most of the time), and hurting diesel's chances against gasoline.

I personally would love to see diesel take off in this country, and there's no question we would be more efficient with it. The question is whether our energy supply chain can keep up with such a switch, and I believe that the answer is no, at least for the med-term.



Correct, US refinery construction will require billions of dollars in investment to keep up with demand. US refinery capacity is currently the longest pole in the tent due to NIMBY-ism and environmental shortsight.

On the bright side, Marathon Oil (MRO) is investing close to $1 billion to upgrade their existing refineries to produce more diesel. The expected lead time is 3 years. I think their forray into this market will be richly rewarded as clean diesel gains market share.


In all this comment, bio-diesel was largely ignored.

We need an interim method of fueling our transportation. (While waiting on nuclear fusion)

Realistically it comes down to Bio-fuels.

After all that is carbon neutral, solar power.


In regards to peak oil, why doesn't biodiedel (and hence high efficiency deisel hybrids) play a part?

Granted, EV's make much more sense, but only for 90% of people's driving. For rural areas, high efficiency biodeisel makes sense. IMHO, I see farmers all over the midwest US using soybean in their crop rotation. The soybean would be used for biodeisel, which the farmers will need to run their tractors. Wouldn't the farmers then use that same biofuel for transportation? They could then rotate that crop (which fixes nitrogen) with their money crop (nitrogen using) of corn, or sugar beets (if the corn subsidy goes away).

Max Reid

When the Diesel prices were lower than gasolene prices, I think that owning a Diesel may be better especially in light of its higher mileage.

But, we have to see how much Diesel (% age) comes out of Crude refining.

If all the vehicles in the World convert to Diesel, what will happen to Gasolene.

If we think this way, Nat-gas, Hydrogen and Electricity may be the neutral fuels.


Both the US military (JP8) and Volkswagen (HCCI) seem to support the idea of a universal fuel for IC engines. Fortunately the major diesel types petro, methyl ester, BTL, nextbtl and perhaps carbon taxed CTL can all be blended. However if you're looking at $2/L or $8/gallon this has to be combined with electrification on several levels such as hybrids and rail replacing truck haulage.



Just about every car on the road has better handling and road feel than nearly any Toyota (save for the now discontinued MR-S, MR2, and Supra). You don't buy a Toyota for buy them for fuel efficiency and reliability.

If you want to know what a well handling car driving experience is like go try a Mazda 3 or the new Mitsubishi Lancer as they will easily out handle the Jetta TDI.


Seems to me a diesel plug in hybrid would be the best way to go. particularly if it is optimized to run bio diesel from algae.
Look into algae bio diesel and it looks quite promising. And with the yields that seem very possible that a nation of mostly diesels is very possible and most probable so that in the longer term, maybe 10 years, diesel could be quite plentiful and quite cheap comparatively.

In the mean time I am slowly saving up my grease from cooking and making biodiesel from it. :) Its taking a while but by the time I purchase my next hybrid, hybrid diesels should be around and I should have a few gallons. I like the idea of traveling on waste breakfast sausage. I only accumulate about a pint a month but it adds up! :)lol


Increasing the use of diesl is a logical step toward making better use of conventional fuels as they are not going away any time soon. I think we will all continue to use fossil fuels to some extent as long as they are available to extract, and although conventional oil may be ready to peak, overall fossil fuels are still very abundant. Unconventional oil, GTL and CTL, possibly with CCS will pick up the slack to fuel the world economy along with some renewables, but since those are all much more expensive, we will need to be smarter about fuel use. One day diesel or maybe designer fuel vehicles with regen braking will be the rule. I think it is evident that maximizing efficiency for liquid fuel vehicles will happen before battery electric or hydrogen is ever a real option.

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