Diesel engines in Mazda cars don't need AdBlue. It's installed just in case

Modern diesel engines, in order to meet restrictive exhaust emissions standards, must be equipped with a DPF filter and SCR catalyst, which require AdBlue fluid to function. This increases production and operational costs, and often leads to problems. Mazda's diesel doesn't need AdBlue, yet still uses it. Why?

The debut of Mazda's Diesel engine caused quite a shock. At a time when car manufacturers are moving away from diesel, some have completely moved on, and others are about to leave combustion cars, the Japanese manufacturer - as if in defiance of all - presented a completely new high-pressure engine with a capacity of as much as 0.87 gallons with six cylinders. Some were scratching their heads, thinking it's madness. Meanwhile, Mazda created an engine so "clean" it doesn't even need AdBlue.

The Mazda CX-60 with a diesel engine does not have the SCR system on all markets, that is, the selective catalytic reduction system for nitrogen oxides. However, in Europe all diesels have SCR and must use AdBlue, including Mazda, which does not need it.

However, as I learned from a Mazda technician, this system was installed in European cars in a sense for peace of mind. There was a risk, after all, that if it were not installed, other manufacturers or environmental organizations might suspect Mazda of some kind of manipulation. Such things have already happened in Europe and beyond. In a word: Mazda would have to prove its innocence.

The key to Mazda's low-emission diesel is... a large capacity. Specifically, the capacity of each of the six cylinders, which is about 0.55 l, or approximately 19.36 cubic inches, is in the upper range of the optimum range, which ranges from 0.45 to 0.55 l or approximately 27.46 to 33.56 cubic inches per cylinder. This makes the engine highly thermally efficient and has a low temperature in the combustion chambers, thus significantly emitting less nitrogen oxides (NOx) than smaller, more burdened engines. The more "stressed out" the diesel engine is, the higher the NOx emissions.

Meanwhile, the Mazda's diesel has a large capacity but low power, reaching a maximum of 254 HP, with a very high torque of 405.66 lb-ft (there is also a weaker version with 200 HP and 331.90 lb-ft of torque). Maximum torque already appears at 1500 rpm.

The engine has only one turbocharger, but it is assisted by a small electric unit which momentarily generates up to 113 lb-ft of torque. Additionally, an extremely precise fuel injection at a pressure of 36,259 psi can utilize up to nine injection doses per work cycle. The engine also has a two-stage combustion chamber, electrically controlled variable valve timing, as well as many solutions aimed at maintaining optimal temperature with a high and low-pressure cooling system.

In practice, this low-stressed engine of a fairly large capacity operates with such ease, and what is associated with this efficiency, that fuel consumption can be in normal road traffic 1.06-1.32 gal/100 miles and not much more at high speeds.

Mazda engineers have gone to give the Diesel engine one last chance. And they took advantage of it. If Mazda today can make an engine that doesn't need an SCR system to meet emission standards, it means there is still a decent reserve. And perhaps we won't have to worry about diesel for a few more years. Unless all that's left is Mazda. Hopefully not.