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Prius Certified to Japanese 2015 Fuel Economy Standards with JC08 Test Cycle

The tougher JC08 test cycle and the older 10-15 cycle. Click to enlarge. Source: ICCT, “Passenger Vehicle Greenhouse Gas and Fuel Economy Standards”

The Prius has become the first car to meet Japan’s new 2015 Fuel Economy Standards, with testing under the new JC08 test cycle.

In December 2006, Japan revised its existing fuel economy standards—which are weight-based—upwards and increased the number of weight bins from nine to sixteen. The JC08 test cycle—which is longer, has higher average and maximum speeds, and requires more aggressive acceleration than the older 10-15 cycle—is due to be introduced in 2010 and will apply to meeting the 2015 standards.

According to the Japanese government, JC08 will increase the stringency of the testing by about 9%, making the new 2015 standards even more exacting compared to the existing standards, for which the 10-15 cycle is used.

The results of the Prius testing reflected the tougher new test cycle: fuel economy under JC08 came to 26.9 km/l (3.7 l/100km or 63.3 mpg US). Under the 10-15 test cycle, the Prius returned 35.5 km/l (2.8 l/100km or 83.5 mpg US). The 2015 target for the Prius weight category (Class 7: 1,196 - 1,310 kg) is 17.2 km/l (5.8 l/100km or 40.5 mpg US).

Japanese 2015 fuel economy targets. Click to enlarge.

A recently published comparison of global fuel economy standards by the International Council on Clean Transportation (ICCT) notes that under the JC08 test, the average fuel economy for the Japanese MY2004 fleet would have been approximately 13.6 km/l (7.4 l/100km or 32 mpg US). The new standard is expected to raise that to 16.8 km/l (6.0 l/100km or 39.5 mpg US), an increase of 23.5%.

The 2015 fuel economy targets range from 22.5 km/l (4.4 l/100km or 52.9 mpg US) for vehicles weighing less than 600 kg up to 7.4 km/l (13.5 l/100km or 17.4 mpg US) for vehicles weighing more than 2,271 kg.




Must be nice to live in a country where the government doesn't shove its head in the sand when dealing with energy and environmental problems.


The problem with this is that if a car does not meet its economy standard, you can make it heavier, move it to a higher bracket and meet that standard.

This is the opposite of what you want.
Perhaps Japanese companies wouldn't do this, but the temptation is there.

It might be better to make the band based on load carrying capacity or passenger volume.

Or just assign cars to bands based on purpose (the way manufacturers do) - but who would have the right to do this.


Don't you think that heavier vehicles normally consume MORE and it is rather difficult to meet stricker consumption standards by increasing the weight of a vehicle.

Too bad that we dont have an International fuel consumption standard expressed in Km/L.

The EEC will certainly come out with something, otherwise the new Japanese standards would be very acceptable.

Rafael Seidl

Mahonj -

you're quite correct, unless the weight brackets and the associated maxmimum fuel consumption rates are very carefully calibrated for the given drive cycle, the temptation to add weight definitely exists. This can of course be countered to some extent by charging road tax based on weight and/or fuel consumption or, by rating a model fully equipped rather than with poverty spec.

The JC08 cycle reflects the low top speeds of Japanese traffic and is not representative of actual driving in the US, let alone Europe. Moreover, the wet Japanese climate means air conditioning is not considered a major factor in real-world fuel economy.

I hope that EU authorities will use the current negotiations about CO2 emissions classes to replace the NEDC with the more representative CADC (Common Artemis Drive Cycle). That would of course lead to numerically higher admissible CO2 limits for 2012, regardless of how they are structured. The public would have to be persuaded that this was a consequence of a change in the test procedure and did not actually imply the industry was being let off the hook. After all, a CO2 metric based on the CADC would better reflect real-world CO2 emissions, which is what really matters. Switching would give politicians a more robust scientific basis for possibly expensive future policy decisions, much like the EPA's updated test procedures will do in the US.

Manufacturers will no doubt gripe that the CADC is much harder to reproduce in business-critical certification testing, especially when using a manual transmission. It should be possible to overcome that with additional operator training and/or a robot manipulating clutch, accelerator and gear lever.

IMHO, an additional test should require the a/c to be switched on with 2 persons inside, after preconditioning the interior with a calibrated heat radiation source simulating a hot summer's day in e.g. the South of Spain, facing the windshield at a specified azimuth angle. Initially, the results of this second test should merely document cool-down rates and the additional CO2 emissions, so consumers can make more informed choices. Once consumers demand - and will pay for - improved climate control technologies such as special glass formulations and coatings, CO2 refrigerant and/or in-cabin CO2 sensors, it may prove useful to start setting a/c-related targets or limits.

In small cars with cheap a/c systems, fuel consumption can go up by as much as 25% when maximum cooling rates are requested. Given the high cost of fuel, many Europeans use a/c as sparingly as possible and also fail to maintain it properly. Some refrigerant is lost over time due to leakage and/or porous hoses. Lack of use is actually bad for the compressor's life expectancy and, more importantly, for traffic safety as heat stress affects concentration levels and reaction times.

Stan Peterson

If you inspect the new Japanese standards, there are several "stop and waits" as if at a stop light. Any vehicle with stop-start would get a synthetic advantage not shared by autos that don't turn the engine off.

Since Toyota is the world's leader in hybrids and a Japanese firm, I sense a rat in the woodpile here...

Rafael Seidl

@ Stan -

I don't how representative the new cycle is of present-day driving conditions in Japan, but cars actually do stop at traffic lights, stop signs and in traffic jams. There is nothing synthetic about the fuel economy advantage that idle stop technology confers on a vehicle.

Roger Pham

Exactly, mahonj,
each band should specify PAYLOAD weight rating, OR INTERNAL AVAILABLE VOLUME, instead of vehicle curb weight, AND the gov. must not loosen the noose too much for higher-capacity vehicles.
This should be a much better incentive for mfg's to lighten up their vehicle.

Those wanting more payload or internal volume must be willing to pay more for the mfg's to use lighter materials such as aluminum in order to meet new and stricter fuel efficiency rating requirement for bigger vehicles.

More and more vehicles from GM and MB and BMW etc. are coming out with mild hybrid with idling stop & start option. This is a very important anti-pollution practice and must be encouraged.

Stan Peterson

I do not criticize a driving cycle that includes 5 "stops and waits" simulating stop lights. I merely wanted people to note that they exist. I noted that the Japanese who boast of hybrids and stop-start vehicles happen to have more of them than others. The Japanese were also notorious for creating import exclusion by regulation, drawn for that purpose.

Presumeably the EU auto makers with an orientation to diesel, will find it more difficult to provide stop-start for their diesels without driving up diesel pollution levels.

I beleive that the diesel, is most efficient when fully warmed up and pretty poor, when temperatures are unequalized. With the very mild EU diesel emission limits of EU4 and EU5 perhaps that won't be a problem. But it WILL bite when EU6 arrives, not to mention real T2B5 or its follow ons.

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