Clean car: the government study that rehabilitates gasoline and diesel


The government released the report’s findings on real-life emissions from gasoline, diesel and hybrid cars this week. An independent study, carried out in real conditions and the results of which do not always go in line with the current political discourse.

In the midst of the controversy over plug-in hybrid cars, the conclusions of IFPEN fall quite well. The study, commissioned by the French Institute of Petroleum and New Energies by the government, is indeed interesting, for three reasons. The first is that it has been driven over several months and using the cars in “real” life, far from European homologation cycles.. The second is that the vehicles chosen already have several thousand kilometers on their counters. So many points that give credit to the conclusions drawn. The third is that the conclusions are not necessarily in line with the current discourse. But impossible for the Ministry of Ecological Transition to back down, he prefers to insist on encouraging the hybrid and the plug-in hybrid at all costs

An independent study without a priori

First of all, we must underline the interest of this independent study, whose desire was to scientifically and analytically compare the environmental performance of gasoline and diesel technologies without taking into account the current environment which points the finger at the automobile as the sole responsible for global climate change. We therefore salute this effort at neutrality. May it put a little truth in an often oriented debate and serve as an additional element of reflection to adjust public policies in the field of automobile taxation. On the other hand, at no time are the models studied directly named.

What to remember from the IFPEN study in 10 points

  1. With rare exceptions, all the models studied meet, in real life, the Euro 6D-Temp emissions standards. Good news on the way in which the famous polluting emission standards are established and the commitment of manufacturers to meet them.
  2. The only models that exceed them on certain severe exercises are those that use the least efficient pollution control technologies. (no particulate filter on gasoline with indirect injection, NOx trap instead of Nox SCR catalyst on diesels). We can therefore see here the importance of using the best available pollution control technologies, which is fortunately in the process of being generalized on Euro 6D Full models.
  3. The efficiency of diesel particulate filters is such that diesels now emit 2.6 times less fine particles than petrol models, even equipped with a DPF. The figure also takes into account the regeneration phases of the DPF.
  4. On the other hand, and this is not a surprise, diesels emit more NOx than gasolines, even if in all cases, the standards are met. Depending on the NOx treatment technology chosen, diesels emit between 10 times more (NOx Trap) and 2.8 times more (SCR with urea injection). Fortunately, this latest technology has a strong tendency to become widespread on Euro 6D-Full models applied for everyone on January 1st.
  5. Gasoline consumes 28% more, resulting in 11% higher CO2 emissions. A figure reduced to + 6% if we also take into account the warming impact of CH4 (methane) and NO2 (nitrous oxide).
  6. Urban use has a significant impact on emissions, particularly that of NOx with an increase of 79% in gasoline and 74% in diesel compared to the average over a full cycle RDE. In addition, city trips mostly include a cold start in real life, a period when pollution control systems are not fully effective. The rise in temperature being longer for the diesels, the latter then take much longer than the gasolines to become “clean”. The study is in line with what we have been saying for years: a diesel car makes no sense if its main use is in the city and / or short journeys. But this technology, now “clean” with modern pollution control systems, retains its full meaning on long journeys and outside the city thanks to its CO2 emissions lower than those of gasoline engines..
  7. The study shows a significant impact of driving style and heavy loads on CO2 and pollutant emissions, which is no surprise.
  8. Emphasis is also placed on the importance of recharging as often as possible for plug-in hybrids, which is also not a surprise. Unfortunately it seems that this is not always the case with their owners …
  9. The study concludes, for hybrid models, zero gain on the motorway, low on the road, but high (approx. 33%) in city use compared to a non-hybrid model. This corresponds to what we see in our ISO measurements. There is however a downside, since only one model has been tested. A sample that is too unrepresentative in our eyes. On our side, we sometimes see more difference in consumption in town, as well as on the road.
  10. Likewise, the study concludes that between a plug-in hybrid and a non-plug-in, the difference in weight – to the detriment of the plug-in – has no impact on consumption and therefore CO2 emissions. But the study only looks at one model. Again, this single sample cannot be sufficiently representative, and cannot reach a formal conclusion.. Especially since this is a Korean model (atmospheric gasoline engine with Atkinson cycle) particularly efficient in this area. Our tests and consumption measurements show, on a much larger sample (we measure almost all the models on the market) that plug-in hybrids indeed very often consume more once the battery has reached its minimum charge threshold, in particular for models equipped with ‘a supercharged petrol unit, which is very common today.

Our conclusions on the IFPEN study

The study therefore indicates that, today much more than yesterday, the choice of the type of engine must really be dictated by the use., because each technology has its advantages and disadvantages. Also, to guide consumers in an objective and neutral way (and not dogmatically as is often the case in the speeches of our decision-makers …), it would be important to make tables available to them, as we do on our site. decision support with usage criteria as inputs, to help them find the best choice for them! In our opinion, it would also be very informative for IFPEN to conduct such an analytical study with engines running on LPG, E85, as well as synthetic fuels, the latter showing great promise.. On the other hand, it would also be necessary to multiply the measures on hybrids and plug-in hybrids in order to have a more representative panel allowing to conclude on their advantages and disadvantages.

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