Left: Frequent operation of an engine under light load can lead to carbon accumulation on piston rings and other components,
which in turn can cause blowby, oil dilution, and poor fuel economy. Top and above right: Valves that are out of adjustment
simply make life hard for an engine. Typically, when this occurs, the engine is unable to draw in sufficient combustion air through
intake valves to completely burn fuel—and unburned fuel is wasted fuel. Expelling exhaust by-products through out-of-adjustment
exhaust valves also is more difficult and equates to still more wasted energy.
lubricating oil can have a deleterious effect on engine
efficiency and fuel economy, not to mention reliability
and longevity. Crankcase oil and transmission fluid
should be changed seasonally or every 100–200
operating hours (and more often in chronically
underloaded engines, as mentioned earlier). This is a
conservative interval, particularly for the transmission.
If the vessel is laid up for the winter, the oil needs
to be changed as part of the winterizing procedure
anyway. Using high quality oil of the correct grade for
the operating environment will ensure maximum lube-oil-related fuel efficiency.
You may consider using synthetic oil, if your engine’s
manufacturer approves of this practice. Synthetic oils
are noted for their ability to reduce fuel consumption
by minimizing internal friction. They are, however,
more expensive than mineral-based oils, so the added
cost and the actual improvement in fuel economy
should be weighed before this approach is permanently
adopted. Synthetic oils have additional advantages over
their mineral-based brethren; look for an upcoming
article in PMM on this topic.
Transmission fluid is relatively inexpensive, and
usually a small quantity is needed. Thus, changing it
with the oil is worth the effort, because this ensures
the transmission fluid is clean and has maximum
lubricity, which translates into minimized friction
and enhanced efficiency. Once again, if allowed by
the transmission manufacturer, synthetic lubricant is
an option that may yield improved efficiency. As the
axiom goes, your results may vary, so make a careful,
performance-based comparison.
Of course, unlike gasoline engines, diesels have no
sparkplugs or ignition system components to wear out.
They do, however, require their own sort of periodic
tune-up. Among the most important of serviceable items
are the injectors. Injectors require inspection, testing,
cleaning, and replacement at intervals mandated by the
engine manufacturer. These intervals vary considerably
from engine to engine, and ignoring or exceeding them
can easily translate into diminished fuel economy. Once
again, for chronically underloaded engines, the injector
service interval must be shortened. When injectors
remain in service well beyond their intended lives, their
