Volvo VNL Operator's Manual page 265

260 Engine Start and Operation
Idling
All engines in the VN models are electroni-
cally governed engines. The idle speed is
pre-programmed from the manufacturer.
Low idle speed is adjustable within certain
limits (for most engines between 600 to 750
r/min). See page 261 for more information.
The common belief that idling a diesel en-
gine causes no engine damage is wrong.
Idling produces sulfuric acid, which breaks
down the oil and eats into bearings, rings,
valve stems and engine surfaces.
NOTE! Avoid excessive idling. If the vehi-
cle is parked for more than 5 minutes, stop
the engine. An engine can burn from 0.75
to 1.5 gallons (3 to 5.5 liters) of fuel per
hour while idling. During long engine
idling periods, the engine coolant tempera-
ture may fall below the normal operating
range*. Incomplete combustion of fuel dur-
ing the warm-up period can cause dilution
of the oil in the crankcase, formation of
lacquer or gummy deposits on the valves,
pistons and rings, and rapid accumulation
of sludge in the engine.
*The Volvo engines are equipped with a
warmholding device (EPG = Exhaust Pres-
sure Governor) to keep engine at normal
operating temperature to prevent incom-
plete combustion, even at idle.