Diesels, gasoline, hybrids, rechargeables: which consumes the least?

At a time when fuel prices are breaking records, each liter of unleaded or less diesel represents a significant saving. However, all the engines on the same vehicle are not equal, very far from it. We even noted big differences, up to three litres, with equivalent bodywork and equipment. Be careful with the choice, despite the enticing promises that are often not kept! And it’s not just the wallet that’s impacted… Because consumption is strictly correlated to CO emissions₂. They are therefore fundamental for the reduction or increase in greenhouse gas emissions. They also dictate the amount of the penalty.

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Plug-in hybrids, it depends on the use

After being strongly encouraged by the public authorities since the two oil shocks of the 1970s because it reduced consumption, diesel is vilified today, following the Volkswagen Dieselgate scandal (in 2015). It even arouses such political and media hatred that zealous city councilors like Anne Hildalgo in Paris have promised to ban it from 2024. And this, even though it does not emit more pollutants than the corresponding gasoline engines since the last Euro 6c depollution standards from 2017-2018 and especially Euro 6d (2020-January 2021). What about hybrids? These are petrol cars equipped with a more or less powerful auxiliary electric motor: the voltage of the electrical circuit is most often 48 Volts in the case of very light hybridization, 200 Volts on average on a fully hybrid car like the Toyota Corolla allowing a range of 2 km in zero emission mode, and downright 350 Volts on a rechargeable Toyota Rav4 type allowing around fifty km in zero emission. In short, not easy to find!

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On paper, plug-in hybrids are necessarily the most economical (if you recharge) since they run for the most part in electric mode. But, once their zero-emission autonomy has been exhausted, they then switch to thermal operation through the gasoline engine alone. The problem: an overweight of 300 kilos because of the batteries! On a 350 km route with mixed road-city-highway use, you can therefore have unpleasant surprises. This is how, on a Peugeot 3008 plug-in hybrid SUV (225 GT at 49,200 euros, -1,000 euro bonus)Challenges registered 8.4 liters of unleaded to the pennies, on average. And at a moderate pace. If we drive flat out on winding and climbing roads, we will easily exceed 10 liters! Against 7.5 liters of diesel on average on an old Blue HDi 180 diesel version.

At Citroën, the C5 Aircross plug-in hybrid SUV (Feel Pack at 44,050 euros), gave us 7.5 liters per cent with more road than with the 3008 but less highway. Against 8.5 liters on the petrol version (130 horsepower) and… 6.3 liters in diesel (also 130 horsepower)! More sober, the equivalent Ford Kuga consumes only 6 liters per cent in the rechargeable hybrid version (2.5 Duratec 225 hp PHEV at 42,900 euros), against 7.5 liters in the simple hybrid, as in diesel. Let’s go back upmarket with the small Renault Captur E-Tech plug-in hybrid SUV (Tekno at 36,950 euros)! During our test, it consumed 5.4 liters on average, against 6 liters for the non-rechargeable hybrid and… 5.5 for the old diesel version, withdrawn from the catalog since. Obviously, rechargeable hybrids are very dependent on their use. On short journeys of a few tens of km with the battery recharged, we obviously fall to 0 liters! An internal Renault study of 22,800 users of the rechargeable Captur E-Tech also shows that 40% of them recharge it one to five times a week and then consume barely 2.8 liters of gasoline on average. .

Very good Toyota and Honda hybrids

Now let’s compare 48 volt hybrid, full hybrid and diesel vehicles with each other! A mini-4×4 Suzuki Vitara (All Grip Style at 32,340 euros) swallowed during our test 6.5 liters of unleaded on average per hundred in its latest fully hybrid Dualjet version, against 6.8 with the 1.4 and 48 volt light hybridization. But, in one case as in the other, these technical innovations supposed to lower CO emissions₂ lead to a degraded result compared to the old diesel version, which required only 6.2 liters of diesel per cent… The consumption of the all-new Honda Civic e: HEV (Advance, 37,100 euros), only available with fully hybrid mechanics, on the other hand proved to be excellent on a restricted test of one hundred kilometers carried out around Madrid, with less than 5 liters per hundred (4.6 exactly). But we did not drive much, it is true, on the 130 motorway, where hybrids shine much less. With a Suzuki Swace (Pack at 31,050 euros), a technical clone of the Toyota Corolla SW, Challenges noted recently, on our usual mixed course of 350 km, 5.4 liters per hundred kilometers. A very good value, better than on the old diesel version of the Corolla.

Let’s finish our comparison with a gasoline-diesel duel, which ridicules the gasoline engine. The latest Peugeot 308 compact sedan (130 horsepower, Feel Pack at 32,070 euros) generated a consumption of 7.7 liters per cent. The same, in diesel of the same power, swallowed 5.8 liters! The gap is even greater for the Citroën C4. The diesel one (Feel Pack at 31,700 euros) was 2.5 liters less at a minimum than the gasoline one.

In summary, diesel remains a safe bet in terms of consumption. Gasoline models appear on this plan disqualified. Hybrids depend. The mild hybridization of 48 volts does not add much to the gasoline engine. Regarding the fully hybrid (non-rechargeable) models, Toyota and Honda technology is very efficient, with very low and satisfactory results, especially in town. But these engines do not like the highway, which stimulates voracity. As for plug-in hybrids, they are only justified if you drive electric daily and make long trips very occasionally. Also, these rechargeables are much more expensive. A Peugeot 3008 Hybrid 225 (Allure finish) costs 46,900 euros, against 39,950 for a diesel version (automatic gearbox) and 37,170 in gasoline (automatic gearbox).