2000 Saab 9-5 Owner's Manual - Page 149

Starting and driving 149 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. 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 consumption. How to read the graph on the right: 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. 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) than stated under "Technical data". Percentage increase in fuel consumption of engine starting from cold compared to engine at normal temperature. Driving technique • To obtain the best running economy, not only regarding fuel consumption but general 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 stationary. IB311