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Engine Start and Operation 217
High Altitude Operation
Engines lose power when operated at high
altitude because the air is too thin to allow
burning as much fuel as at sea level. For
naturally aspirated engines, this loss is
about 3 percent per 1000 feet (300 m) in-
crease in altitude above sea level. Most
turbocharged engines are rated for higher
altitudes and will not lose as much power
as a naturally aspirated engine.
An engine will produce excessive exhaust
smoke at high altitude unless a lower gear
is used. Shift gears as needed to avoid ex-
cessive exhaust smoke.
Closely monitor the gauges during high al-
titude operation. The thinner ambient air
reduces the efficiency of the engine cooling
system. Engine overheat or cylinder dam-
age could occur if the engine is operated at
full load for extended periods at high alti-
tudes in hot weather. Downshift and reduce
vehicle speed to reduce engine load when
driving on long grades in these conditions.
This will help keep engine air intake mani-
fold and coolant temperatures within safe
limits.