Why Do Your Miles Per Gallon Not Match the EPA Estimates?
Allen Teal
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We've all seen it. The sticker in the window tempting us to buy this fuel efficient shiny new toy. We may have been enticed to trade a large comfortable SUV for a much smaller commuter vehicle. Compared to the SUV, this car is stingy in the fuel consumption area. Compared to the sticker in the windo 
w, it's nowhere near its press releases. That 50 mpg has become a realistic 35 mpg. While happy with the savings, our spirits sag as buyer's remorse sets into our mood.
So, why isn't our much smaller vehicle living up to its billing? In some ways it's the same reason that horse racing requires every horse to carry the same weight. The race is only fair if every animal is asked to run the same distance hauling the same load. Vehicle fuel tests are uniform. Each car travels the same course carrying the same load under similar conditions. The estimates are intended to give a picture of the economy of each car relative to its competition.
You ask your car to perform many tasks that the EPA didn't. If you're a fan of jackrabbit starts, they're not fuel efficient. Do you like to warm your car up before you drive it? That's not fuel efficient either. Is your car left idling while you unload or load passengers or things? You're consuming fuel without adding miles. If you speed down the freeway, it uses more fuel than driving the speed limit or less.
Your car is driven up and down hills and over rough road surfaces. These cut into your car's efficiency as do gravel roads. Continuously running your air conditioner or driving in all temperatures and weather conditions affect gas mileage. None of these are factored into that sticker. At least, not enough of them to help you.
If you tune your car up and change the oil every 5 years or so whether it needs it or not, this will hurt your gas mileage. The octane level of your fuel will change your cars fuel usage. The number of passengers, what you carry in the trunk, or tow behind you will cause miles per gallon to fluctuate.
So, why isn't our much smaller vehicle living up to its billing? In some ways it's the same reason that horse racing requires every horse to carry the same weight. The race is only fair if every animal is asked to run the same distance hauling the same load. Vehicle fuel tests are uniform. Each car travels the same course carrying the same load under similar conditions. The estimates are intended to give a picture of the economy of each car relative to its competition.
You ask your car to perform many tasks that the EPA didn't. If you're a fan of jackrabbit starts, they're not fuel efficient. Do you like to warm your car up before you drive it? That's not fuel efficient either. Is your car left idling while you unload or load passengers or things? You're consuming fuel without adding miles. If you speed down the freeway, it uses more fuel than driving the speed limit or less.
Your car is driven up and down hills and over rough road surfaces. These cut into your car's efficiency as do gravel roads. Continuously running your air conditioner or driving in all temperatures and weather conditions affect gas mileage. None of these are factored into that sticker. At least, not enough of them to help you.
If you tune your car up and change the oil every 5 years or so whether it needs it or not, this will hurt your gas mileage. The octane level of your fuel will change your cars fuel usage. The number of passengers, what you carry in the trunk, or tow behind you will cause miles per gallon to fluctuate.
- Your driving pattern will affect gas mileage.
- Warming your car before driving uses gasoline without adding miles to the formula.
- Hauling additional weight or towing reduces gas mileage.