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Comparing Accords: Diesel, Hybrid and Gasoline


After posting about the Honda clean diesel ad (earlier post), I decided to do some quick  side-by-side comparisons using three models of the Honda Accord: the Accord Diesel featuring the new, clean 2.2 i-CTDi engine touted in the ad (picture at right), the new Accord Hybrid, and two gasoline sedans. The outcome: the Accord Diesel (using petroleum diesel) offers the lowest fuel consumption and the lowest CO2 emissions, even surpassing the Accord Hybrid.

In a sense, it’s not a fair comparison—the cars, even though they are of the same model family, target different consumers with different levels of performance and features. (Furthermore, the diesel isn’t offered in the US.) Honda opted to create a performance hybrid with its Accord, thereby somewhat reducing the fuel consumption and CO2 emissions benefits. Had the company implemented its IMA hybrid drive with a smaller, more efficient gasoline engine, the results would be much better.

Nevertheless, the comparison across different powertrains in the same model is interesting. The table below compares the Accord Hybrid, the Accord Diesel 2.2 i-CTDi Sport, the EX Sedan and the LX V-6.

  2005 Accord Hybrid Sedan 2005 Accord i-CTDi Sport 2005 Accord EX 2005 Accord LX-V6
1.  Grams CO2/km for all vehicles except the diesel estimated by using a factor of 19.36 pounds CO2 per gallon of gasoline (2.32 kg/liter). Actual result will vary with driving pattern, fuel composition, and so on.
Fuel Gasoline Diesel Gasoline Gasoline
Type V-6 I-4 I-4 V-6
Displacement (liters) 3.0 2.2 2.4 3.0
Power: kW
Torque: Nm
BMEP (psi) 191.1 281.5 169.0 174.6
Electric Motor        
Power Output (hp) 16
Torque: Nm
Acceleration 0-60 (seconds) 7.5 9.3 9.4 8.0
Combined mpg (US)
CO2 g/km1 165 143 188 227

Comparing the i-CTDi and the EX highlights some of the efficiency and benefits of the diesel platform. Although the gasoline engine is slightly larger, the diesel offers incrementally better acceleration (due to the greater low-rpm torque), 33% better fuel consumption and approximately 25% less CO2.

The amount of CO2 emitted by a car is dependent on the composition of the fuel burned, the completeness of the combustion, and the total amount of fuel consumed. Gallon for gallon, diesel fuel will produce more CO2 than gasoline—but because diesels tend to be more fuel efficient, a diesel delivering equivalent performance to a gasoline engine will produce less carbon dioxide than its gasoline counterpart—exactly what we see in the table above. A diesel engine burning a biodiesel blend will improve upon that even more dramatically.

By maintaining a larger engine in the Accord Hybrid to optimize power and performance for the driving experience, Honda traded off some potential gains in fuel economy and CO2 emissions.

Honda offers a terrific animated introduction to the technology of the diesel i-CTDi here. It’s well worth the look if you are interested in how Honda designed and engineered this engine.



Here is the article that talks about Diesel in the US market

Since you like the diesel commercial so much and
In case you haven't seen the Honda Cog commercial

John Norris

But is the diesel SULEV? (I assume the hybrid is). We're choking here in Europe on diesel PM emissions. Gasoline hybrids seem to deliver the best combination of low CO2 and better air quality. Have you seen how VW's "clean" diesel scores on the EPA air quality scale? 1 out of 10.

-- John


Re: the diesel PM emissions, yes, I’ve seen that, and seen the additional research talking about the health impact.

Actually, the Accord Hybrid is not SULEV. It’s LEV II-ULEV or EPA Tier 2/Bin 5. The i-CDTi is Euro IV compliant, which is not as stringent on PM and NOx as Tier2/Bin 5. So yes, the hybrid is better than the i-CTDi from PM/NOx point of view.

Adjusted to g/km, here are the different PM standards:

Tier 2/ Bin 5 PM: 0.006 g/km
SULEV PM: 0.006 g/km
EURO IV PM: 0.025 g/km

The Euro IV standard is twice as restrictive on PM as the earlier Euro III (2000): 0.025 vs. 0.05.

Euro V regulations are coming out next year for implementation in 2010, I believe.


Try taking a drive in the uplands of Haute-Savoie, home of big mountains and frugal, diesel-loving peasant types. The blue haze is extremely evident!

Mikhail Capone

One would hope that Honda will not limit itself to the "halo" Accord and will produce hybrids with 4 cylinder engines.

What are the chances of the Diesel Accord coming to North-America? Any plans for that yet?


Honda already has a 4-cylinder hybrid: the Civic. (earlier post) And as you’d expect, the emissions and fuel consumption results are better than than of the Accord...but it doesn’t perform as well.

They are trying to balance two different sets of buying criteria, and experimenting with different ways to do that. The Insight was maximum efficiency (but didn't sell well); the Civic Hybrid was supposed to be for mass appeal, and it is doing ok, but not as well as the Prius. The Accord is their current attempt at striking that balance between efficiency, performance and luxury.

The Autoweek article anon points to above ( describes Honda’s current state of thinking about diesels in North America:

Honda has no immediate plans, but its engineers are confident that they can reduce harmful emissions from the company’s diesel engines to meet stringent U.S. standards.

Honda Motor CEO Takeo Fukui supports the effort. “There would be room in America for a diesel vehicle to get in” he said at a company press event here last week.

So when they can clean it up some more to meet the US standards, sounds like they’ll try.


Interesting that there isn't any comparision to the Honda GX (compressed natural gas). It is the 'cleanest car on Earth.' There are no "clean diesels" It's time this country looked at domestic sources and a fuel that can better transition to the hydrogen economy.


The GX is a Civic. :-) I thought after the quick comparison of the the Accord models, I’d tackle the Civics next—Hybrid, Gasoline, Diesel and Natural Gas.

With the growing import gap with natural gas, though, I don’t think you can refer to it as a domestic source anymore than you can oil. The US has been a net importer for more than 35 years, with the gap growing wider.

That’s why the focus on LNG.

John Norris

Mike, thanks for the SULEV-Tier 2/Bin 5 data. Very helpful. Maybe SULEV-level PM in a diesel would be easier using say B20, thereby killing multiple birds with one stone. Still got the NOx problem though. I live in the UK and we're a little behind the rest of Europe in getting biodiesel going (it's unobtainable, at any blend, in my area). It would be interesting if manufacturers specified their cars would meet SULEV and CO2 targets but only if running on B20 or better!

-- John

John Norris

FYI, from the EPA site:

2005 Jetta Air Pollution Score:
Diesel (non-California) = 4/10
Gasoline (California) = 10/10


-- John

Mikhail Capone

Mike, I know about the Civic hybrid but I think it would be nice for those who need a bigger car, like the Accord, to be able to choose something less expensive than the V6 top-of-the-line model.

Still, it's a step in the right direction for Honda. Now for the Camry hybrid!


very disappointed in performance of my new accord hybrid. getting lower mileage than camry i replaced it with. anyone having better luck or anyone finding a solution to weak performance? my dealer doesn't seem to have a clue


Why not add the Honda FCX Concept to your comparison matrix? It's dimensions and power output are very similar to that of the Honda Accord.


I'm reading a lot about the non CO2 emissions from diesel here -- but isn't that assuming that you would be running the car on regular petro-diesel? Aren't those figures a lot lower if you run your vehicle on biodiesel?


Do you have ANY idea about the cost of the diesel?
Also I would like a coupe because if I get a sedan I'd have to buy a 4000 WC LIFT to go on the roof!

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Any idea when the 2.2 i-ctdi will release in canada?

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