Diesel engines are highly reliable, durable and are used for a
wide range of applications with low fuel usage owing to its higher
thermal efficiency compared to other mobile power sources.
Heavy-duty diesel engines are used for both on-road and off-road
applications and dominate the heavy-duty engine segment of the
United States transportation market. Due to their high reliability,
there are considerable numbers of on-road legacy heavy-duty diesel
engine fleets still in use in the United States. These engines are
relatively higher oxides of nitrogen (NOx) and particulate matter
(PM) producers than post 2007 model year diesel engines. There have
been various emission certification or verification programs which
are carried out in states like California and Texas for different
aftermarket retrofit devices, fuels and additive technologies for
reducing NOx and PM emissions from these legacy diesel engines.
During these programs, emissions from a candidate technology
configuration are compared to a baseline condition using a
representative legacy engine. However, under laboratory test
conditions, a small variation in the measurement of emissions can
lead to either passage or failure of the candidate technology. This
research study investigates how engine oil aging history in a
legacy engine affects the emission levels which may cause these
decisive small variations.
A 12.7L 1992 Detroit Diesel Series 60 legacy heavy-duty diesel
engine was tested in an engine dynamometer test cell over 40 hours
using commercially available Shell Rotella®-T SAE 15W-40 engine oil
in two separate test campaigns. Gaseous and particulate matter
(mass-based and particle number concentration) emissions were
measured during the aging period. Oil samples collected at
different aging stages were analyzed for changes in its physical
properties along with ash content, soot contamination, and metal
content. Additionally, the oil samples were analyzed for
determination of particle size distribution of suspended particles
in the samples using a novel technique.
The results obtained showed no significant changes in regulated
gaseous and PM mass emissions during either of the test campaigns
that can be attributed to the lubricant oil aging within the first
40 hours. Analysis of the oil samples showed no significant change
in viscosity or density within the aging time period, but showed
significant change in total acid number (TAN), soot content, metal
content, and total base number (TBN). Investigation into particle
sizing of suspended particles in the oil samples suggested
contamination of the oil by larger diameter particles during the
initial 15 hours of its use compared to particles found from the
oil samples from the later part of the aging time period. It was
concluded that oil aging does not affect regulated emissions
generation during the short time duration typically experienced
during a fuel or retrofit device evaluation.