StevenFromTexas,
I know that not every thing below applies, but here are some things that can reduce your fuel economy.
Quick acceleration and heavy braking can reduce fuel economy by up to 33 percent on the highway and 5 percent around town. New EPA tests account for faster acceleration rates, but vigorous driving can still lower MPG.
Frequent accelerator pedal movement will reduce fuel economy because of fuel enrichment during the periods of acceleration. Under such driving conditions the torque converter clutch (tcc) also disengages, contributing to fuel economy losses.
Excessive idling decreases MPG. The EPA city test includes idling, but more idling will lower MPG.
Driving at higher speeds increases aerodynamic drag (wind resistance), reducing fuel economy. The new EPA tests account for aerodynamic drag up to highway speeds of 80 mph, but some drivers exceed this speed.
Cold weather and frequent short trips can reduce fuel economy, since your engine doesn't operate efficiently until it is warmed up. In colder weather, it takes longer for your engine to warm, and on short trips, your vehicle operates a smaller percentage of time at the desired temperature. Note: Letting your car idle to warm-up doesn't help your fuel economy, it actually uses more fuel and creates more pollution.
Cargo or cargo racks on top of your vehicle (e.g., cargo boxes, canoes, etc.) increase aerodynamic drag and lower fuel economy. Thus, hang-on luggage carriers, cat toppers, open windows and/or open trunk, etc results in less fuel economy. MPG tests do not account for this type of cargo.
Running electrical accessories (e.g., air conditioner) decreases fuel economy. Operating the air conditioner on "Max" can reduce MPG by roughly 5-25% compared to not using it. Electrical loads, (headlights, heated back glass...) also result in lower fuel economy, (typically less than 1 mpg difference, each 10 amps takes approximately .4 mpg).
Driving on hilly or mountainous terrain or on unpaved roads can reduce fuel economy. The EPA test assumes vehicles operate on flat ground.
Road surface condition impacts fuel economy. Gravel and/or pot holed roads decrease fuel economy. Hills (vs. level terrain) also negatively impact fuel economy. Even gradual imperceptible increases in elevation result in real measurable decreases in fuel economy. Similarly, driving in the rain or snow decreases fuel economy.
A poorly tuned engine burns more fuel.
Improperly aligned or inflated tires can lower fuel economy by increasing rolling resistance. Harder tires, (more air pressure, or different tire compositions) result in better fuel economy. Do not exceed maximum pressure as labeled on the tire, typically 30-35 psi. The disadvantage of this is that the greater the tire pressure, the harsher the vehicle ride.
A dirty air filter can make your engine work harder.
Brake drag (even a minimal amount undetectable by coasting) can have a significant negative impact on fuel economy.
Vehicle suspension misalignment can cause poor fuel economy, new tires, tire rotation, and/or front end alignment may be required to correct fuel economy.
Performance tires and/or tires with larger "contact areas," (like 60 series aspect ratio), can cause as much as 3 mpg lower fuel economy when compared to hard "thin" tires. Find out if the tire size currently on the car is the same as original equipment. Replacement tires taller than original equipment tires cause the odometer to read less than actual distance traveled. This will result in lower calculated fuel economy than actual fuel economy.
Thank you,
Elizabeth GM Customer Service
