Factors That Affect Fuel Economy

FACTORS THAT AFFECT FUEL ECONOMY:

BRAKES
Brake drag can have a significant negative impact on fuel economy. A misadjusted stop lamp switch or parking brake or riding the brakes can cause the brakes to drag.

DRIVING HABITS
Frequent short trips (less than five miles), especially in cooler ambient temperatures (less than 65°C [149°F]), will necessitate fuel enrichment on start-ups, especially after "soaks" with the engine off for approximately a half hour or more.

Frequent accelerator pedal movement while driving will reduce fuel economy because of fuel enrichment during the periods of acceleration. Under such driving conditions the torque converter clutch (TCC) may disengage, contributing to fuel economy losses. Prolonged idle periods reduce fuel economy especially in cold ambient temperatures when vehicle is allowed to "warm-up".

FUELS
Using fuels of a lower octane than the vehicle was calibrated to will cause increased knock sensor system activity. This will result in a net decrease in spark advance and thus poorer fuel economy. Using fuel of a higher octane than the vehicle was calibrated for will not increase fuel economy.

Variations in how much fuel is added to the fuel tank during re-fueling can greatly affect calculated fuel economy. These effects decrease as the distance traveled and the number of tank fill-ups increase.

NEW ENGINE
New vehicles have not yet had an opportunity for the engine to break-in (rings to seat, etc.). A typical engine will take three to five thousand miles to break-in and during this time period a gradual increase in fuel economy can be expected.

PARASITIC LOADS
Air conditioning and/or electrical loads (headlamps, heated rear defogger, etc.) also result in lower fuel economy.

ROAD CONDITIONS
Road surface condition impacts fuel economy. Gravel and/or pot-holed roads decrease fuel economy, hills versus a level terrain also negatively impacts fuel economy. Similarly, driving in the rain or snow decreases fuel economy.

SUSPENSION
Vehicle suspension misalignment can cause poor fuel economy. Check all four tires for abnormal and/or premature tire wear, which may indicate vehicle misalignment or a need for tire rotation.

TIRES
The original equipment Saturn tires were designed to optimize tread life, fuel economy, ride handling, and other performance characteristics. Tires with specifications different than the original tires (i.e. size, etc.) may not perform equally in one or more tire performance parameters.

TIRE PRESSURE
Underinflated tires can reduce fuel economy. Refer to the Vehicle Tire Loading Information Label for correct inflation pressures.


TRANSAXLES
Driving an Automatic in D3 gear rather than D4 gear or a manual in 4th gear rather than 5th gear at highway speeds typically results in a 3 to 5 m.p.g. penalty. Also on manual transaxles, if you drive with your foot on the clutch fuel mileage will decrease.

VEHICLE WEIGHT
Each 125 lbs. of additional weight results in a 0.3 m.p.g. loss of fuel economy, thus additional passengers, luggage, etc. will decrease fuel economy.

VEHICLE WIND RESISTANCE
More wind "drag" means less fuel economy. Thus, hang on luggage carriers, car toppers, open windows, open sunroof and/or an open trunk mean less fuel economy.