Why is my gas mileage going up and down?

A bad fuel injector or dirty/old fuel filter can drastically affect the flow of fuel into the engine. A fuel system problem is one of the most common causes of poor gas mileage. The more you run your A/C, the lower gas mileage you will get.

Why does the gas gauge in my car fluctuate?

Older cars have a float that sends an analog signal to the gauge, typically it is a voltage that simply indicates where the float is at on the resistor unit in the tank. It will fluctuate when the gasoline in the tank sloshes, and the float bounces around. It can be a defective sending unit located in the gas tank.

Why does the price of gasoline go up and down?

This cost is the primary factor that influences the price of retail gasoline year-round. Refinery costs, which also fluctuate throughout the year, represent another expense that impacts gasoline prices. Gasoline is blended differently in the summer to reduce the amount of smog-creating pollutants that enter the environment through fuel.

How to increase mpg and increase gas mileage?

According to fueleconomy.gov, the habit of hard braking can decrease your gas mileage anywhere from 15% to 30% on the freeway and 10 to 40% in city traffic. You can increase your BMW MPG by avoiding sudden stops and braking gradually but safely.

Why does fuel economy vary from Gallon to gallon?

The biggest fluctuation occurs because ethanol, which is blended with gasoline in varying amounts, contains less energy. “When you fill up, you are paying for a gallon of gas, but the energy in that gas varies significantly,” Clark says.

Why does the fuel economy gauge fluctuate so much?

Clark says the gauge is “dead nuts accurate” — if you consider all the variables at work during driving, including temperature, driving conditions and driving style. The biggest fluctuation occurs because ethanol, which is blended with gasoline in varying amounts, contains less energy.

How does excessive idling affect your gas mileage?

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.

How are MPG ratings different from average fuel consumption?

There’s an important distinction to make here. EPA fuel economy ratings are only an estimation of average fuel consumption for a given type of driving, and many cars come with an average fuel consumption display. That display shows the average fuel consumption over a given period of time.

How does driving at high speeds affect your 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.