Page 44 - Energize August 2021

TECHNICAL

Diesel emissions – A breath of

fresh air (Part 2)

by Steven Lumley, WearCheck

This article – the second of a two-part series – continues the discussion around reducing air pollution
through stricter diesel engine emission standards and techniques. Here, we examine the intricacies of
appropriate lubricant viscosity as well as the performance criteria of a range of additives and how they
contribute to the war against harmful emissions, or not.

n Part 1, published on page 42 in the July issue of Energize, change the appetite of the diesel engine.
we looked at the various diesel emissions produced, the laws Change begets change, and with new engine design and the
Igoverning them, and the technologies utilised to limit these addition of new emission control technologies, naturally comes
emissions in mitigation of green-house gases and the pursuit of changes to the fuels and lubricating oils we have to use as well as
better air quality. Now, we look at how all these developments will the addition of new fluids in these “greener” engines.
To understand the changing appetite of the beloved workhorse,
Abbreviation Definition the diesel engine, we must look at the market drivers shaping this
shift in appetite: better emission system compatibility, improved fuel
API American petroleum industry economy and greater engine durability.
ASC Ammonia slip catalyst Fuel and lubricant manufacturers play a key role in achieving
C-DPF Catalysed diesel particulate filter
these drivers. Engine oils and fuels are no longer viewed as merely
DEF Diesel exhaust fluid
a consumable, but rather an integral component of the engine,
DOC Diesel oxidation catalyst
having just as much importance as the hardware itself, and with
DPF Diesel particulate filter
good reason – they have an incredibly hard job to perform. Engine
EURO European emissions standards
tolerances, along with increased complexity and performance
EGR Exhaust gas recirculation
expectations, create an environment of increased stress in which
FM Friction modifier
HTHS High temperature high shear fuels and lubricants operate.
HC Hydrocarbons
LNC Lean NOx catalyst Improved fuel economy
NAC NOx adsorber catalysts Lubricant manufacturers make use of multiple complex physical and
PM Particulate matter chemical strategies to improve fuel economy – the most common of
PAH Polycyclic aromatic hydrocarbon which is to reduce the viscosity of the oil, which often necessitates
SCR Selective catalytic reduction the selection of higher quality base oil, combined with the use of
SOF Soluble organic fraction additives like viscosity index improver and friction modifiers.
SAPS Sulphated ash, Phosphorus, Sulphur
TBN Total base number
VII Viscosity index improver
ZDDP Zinc dialkyl dithiophosphate

Symbol Name

NH₃ Ammonia
CO₂ Carbon dioxide
CO Carbon monoxide
NO Nitric oxide
NO₂ Nitrogen dioxide
N2 Nitrogen gas
NOx Nitrogen oxides
SO₂ Sulphur dioxide
Table 1: Commonly-used abbreviations and symbols Dispersant additive

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