Why Am I Getting Bad Gas Mileage?

Have you noticed a recent drop in your vehicle’s fuel economy? Does it seem like you’re filling up at the gas station more frequently? Has the cost of your weekly commute begun to eat into your budget for other essentials? We’re here to help! This article takes a look at a wide range of factors that may be effecting your car’s average gas mileage. These factors can be divided into three basic categories: driving conditions, environmental conditions, and vehicle condition.

Your fuel economy is a result of many elements on any given day. A change in traffic, the route that you follow, weather (whether inclement or not), and your vehicle’s state of tune can have a significant effect on the amount of cash you drop at the pump each month.

Driving Conditions With a Negative Effect on Gas Mileage

• Stop and Go Traffic – Combine idling with repetitive spurts of acceleration and braking and what do you get? A whole lot of wasted fuel. Has your commute become even more clogged? Can you find an alternate route?
• Excessive Idling – Avoid idling whenever possible. Can you endure a few minutes without the air conditioner or heater running? Can you park it and run inside, rather than sitting in the drive-up?
• Vehicle Speed – Every vehicle has a sweet spot – a cruising speed where it is most fuel-efficient. A difference of five or ten miles per hour can make a noticeable impact. You can test this by resetting your vehicle’s average fuel economy gauge at different speeds on a long highway run.
• Excessive Lane Changes – Pick a lane on the highway, stick with it, and go with the flow. Every time you accelerate to change lanes, you burn extra fuel.
• Terrain – This one’s simple to grasp … think about how much work it is to climb those hills on a bicycle and how fast you roll on the way downhill. Have you changed your standard commuting route?

Weather Conditions That Cause Poor Gas Mileage

• Hot Weather – In and of itself, hot weather isn’t necessarily a bad thing for fuel economy. Turning on the air conditioning is the culprit. Every car reacts differently to A/C usage. With some vehicles, the hit can be substantial. With others, it’s relatively small. Nothing to due on a hot August afternoon? Try some A/C on/off tests with your car to see how it fares!
• Cold Weather – effects gas mileage in a number of ways: increased idle time (to warm up), decreased efficiency until warmed up, increased use of defrosters (with A/C), increased use of cabin, seat, and steering wheel heaters create drain on the electrical system, which in turn creates drag on the engine. If possible, limit the amount of warm up time and go easy for the first few miles.
• Rain and Snow – Do decreased traction and increased rolling resistance effect fuel economy? You bet they do. If your tires have lost traction, gas mileage will suffer.
• High Humidity – When the weather turns humid, we turn on the A/C … often just to defog the windshield. This lowers MPGs.

Vehicle Conditions That Cause Bad Gas Mileage

• Brake Drag – Any excess drag in the braking systems (whether the normal brakes or parking brake) will increase rolling resistance.
• Poor Alignment – Do you have uneven tire wear? Misaligned wheels cause increased rolling resistance.
• Oxygen Sensors – Bad O2 Sensors are notorious for their effect on fuel economy.
• Fuel System – Clogged injectors can be culprit. A fuel system clean on older vehicles is money well spent.
• Tire Type – Choose an aggressive set of tires and you’ll see your MPGs drop. Choose a set of state-of-the-art low-rolling-resistance tires and your MPGs may climb.
• Tire Inflation – Do those look low to you? Keep your tires aired up to the PSI suggested on the sticker inside your driver’s door (or in the owner’s manual). You usually can go a bit higher, but never higher than the limit listed on the tire sidewall for safety’s sake. Higher tire pressures will increase ride harshness and center-of-tire wear.

Check Fuel Economy by Vehicle …

– by Daniel Gray