Saab 2001 9-3 - Manual (Page 176)

176 Starting and driving
Economical motoring
Factors affecting fuel consumption
Fuel consumption is greatly affected by the
general driving conditions, the way in which
the car is driven and at what speeds, the
weather, the state of the road, the condition
of the car, etc.
Breaking-in
Fuel consumption may be somewhat higher
during the break-in period (the first 3,000–
4,000 miles (5,000–7,000 km).
Weather conditions
Fuel consumption can be as much as 10 %
lower in summer than in winter. The higher
consumption in cold weather is explained by
the longer time it takes for the engine to
reach normal operating temperature, and
for the transmission and wheel bearings to
warm up. Fuel economy is also affected by
the distance driven: short journeys of
3-5 miles (5-8 km) do not give the engine
enough time to reach normal temperature.
Strong winds can also affect fuel consump-
tion.
How to read the graph:
If fuel consumption with the engine at
normal temperature is 28 mpg
(10l/100 km), the actual fuel consumption 3
miles (5 km) after the engine has started
from cold will be:
– 23.5 mpg (12l/100 km) at outside temp.
of 68°F (20°C) (increase of 20%)
– 17.7 mpg (16l/100 km) at outside temp.
of 32°F (0°C) (increase of 60%)
– 14 mpg (20l/100 km)) at outside temp. of
–4°F (–20°C) (increase of 100%)
As can be seen, both the distance travelled
by the car and the outside temperature have
a major impact on fuel consumption after
the engine has started from cold. Thus, if the
car is mainly used for short journeys of
3–5 miles (5–8 km), the fuel consumption
will be 60–80 % higher than normal.
Driving technique
• To obtain the best running economy, not
only regarding fuel consumption but gen-
eral wear also, regular service is required.
• High speed, unnecessary acceleration,
heavy braking and much low gear work all
gives rise to higher fuel consumption.
• Frequent gear changing in traffic, starting
in cold weather, the use of studded tires
and roof racks, and towing a trailer all
increase fuel consumption.
• Do not run the engine when the car is sta-
tionary.
If idling, it will take much longer before the
engine becomes hot. Engine wear is
greatest during this warming-up phase.
Therefore drive away as soon as possible
after the engine is started and avoid high
revving.
IB311
Percentage increase in fuel consumption
of engine starting from cold compared to
engine at normal temperature