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Why Your Gasoline Won’t Take You As Far As it Used To

Why Your Gasoline Won’t Take You As Far As it Used To thumbnail

Over the weekend, I saw a passing reference on Twitter to the declining energy content of gasoline. Intuitively I know this to be correct for reasons I discuss below. But the poster linked to data from the Energy Information Administration (EIA) that I hadn’t previously seen.

The EIA doesn’t directly tabulate the energy content of gasoline. But they do provide two pieces of data that let us calculate it ourselves from two relevant tables in the April 2019 Monthly Energy Review.

Table 3.5 provides Petroleum Products Supplied by Type in thousands of barrels per day, while Table 3.6 provides Heat Content of Petroleum Products Supplied by Type in trillion Btus per year.

From the annual numbers, doing the appropriate conversions (which includes accounting for leap years) provides the energy content of gasoline, in BTUs per gallon, since 1949. What we find is that the EIA reported a constant energy content of gasoline from 1949 to 1992 of 125,071 Btu/gallon. I have always typically used 125,000 Btu/gal as the standard value for gasoline.

(Click to enlarge)

The energy content of gasoline

Starting in 1993, the EIA shows the energy content start to decline. The decline accelerates in 2006. What happened then? I have seen two explanations floated.

I have heard some suggest that the shale oil boom in the U.S., which created an abundance of light oil, ultimately lowered the BTU value of gasoline. This is unlikely for a couple of reasons.

First, to change the energy content of gasoline you must change the composition. As I explained in a previous article, adding butane is a recipe change that takes place seasonally. It impacts the vapor pressure of the gasoline, but it also impacts the energy content. Butane has an energy content of 103,000 BTU/gal, so the more butane, the lower the energy content of the gasoline blend. This means that winter gasoline, which contains more butane, has a lower energy content.

But the other reason that shale oil can’t be the culprit is that U.S. oil production didn’t start to move higher until 2009. By then, the EIA was already reporting that U.S. gasoline’s energy content had fallen to 121,167 BTU/gal.

Here’s the real culprit:

(Click to enlarge)

The impact of ethanol blending on the energy content of gasoline

The 2005 energy bill gave us the Renewable Fuel Standard (RFS), which mandated that an increasing amount of ethanol had to be blended into the fuel supply. As the mandate ramped up, so did ethanol production. In turn, the energy content of gasoline declined.

As was the case with butane blending, adding ethanol is fundamentally changing the recipe of gasoline. The energy content of ethanol is 76,000 Btu/gal, so as ethanol blending ramped up, the energy content in a gallon of gasoline fell.

But we also know ethanol is the reason because the EIA table actually includes the footnote: “Beginning in 1993, also includes fuel ethanol blended into motor gasoline.”

To be clear, it’s not a huge decline in energy content. It’s about 4% across the national gasoline pool (~140 billion gallons per year), and it is masked somewhat by the rising fuel economy standards of automobiles.

Falling energy content in gasoline has a couple of implications. One is that most vehicles will now require more gasoline to travel the same distance. In other words, fuel efficiency will have declined along with gasoline’s energy content.

But the other is that today’s daily consumption of 9.3 million barrels per day of gasoline is equivalent in energy terms to the consumption of 8.9 million barrels per day 20 years ago. Or, another way to think of that is that if we were consuming the same number of gallons of gasoline as we were 20 years ago, our energy consumption would have declined.

I will note one more item in conclusion. It is clear, given the consistency of the EIA data, that they are just calculating an energy content. If they were actually taking measurements, we would see more variability.

Further, I looked at the monthly values over the past year, and the EIA numbers for the energy content of gasoline are the same in summer and winter. This isn’t correct, which means they are simply using calculated numbers that average the energy content out over the entire year.

By Robert Rapier


9 Comments on "Why Your Gasoline Won’t Take You As Far As it Used To"

  1. Sys1 on Sun, 5th May 2019 11:08 am 

    I’ve never heard about that, so great article!

  2. Pete Bauer on Sun, 5th May 2019 12:47 pm 

    Basically the energy content in gasoline has fallen from 125,000 BTU to 121,000 BTU which is decline of 2%. That’s perfectly OK.

    Winter gasoline has 10% Butane content and this hydrocarbon is available in plenty because of shale gas.

    Year round gasoline has 10% Ethanol content and this is another good thing as it provides farm jobs.

    Both Butane C4 hydrocarbon and Ethanol C2 alcohol are much cleaner fuels and its good. Also the Ethanol content is slowly increasing with more people using E15 fuel.

    Even oil drilling companies are cutting down diesel by using a new concept called “Electric Frack” which basically uses the natgas from shale wells to power the drilling equipment instead of diesel.

    They save a lot of money because the gas used will otherwise be flared. They also reduce the pollution. Cutting cost is another important factor for them.
    Why is it called “Electric Frack”, because natgas powers the electric turbines instead of mechanical ones.

    Everyone wants to reduce diesel.

  3. Pete Bauer on Sun, 5th May 2019 1:38 pm 

    Slight correction, a decline of 3.2% and not 2%.

    China which has 6 million NGVs (CNG & LNG) is now going full speed into Methanol, an alcoholic fuel with 1 carbon atom.

    Geely automotive has launched heavy duty trucks capable of running on 100 % Methanol fuel.

    Methanol can be obtained from natgas, coal or wood and is much cheaper on energy terms than gasoline/diesel.

  4. Pete Bauer on Sun, 5th May 2019 1:47 pm 

    Hah, the big oil is spreading lies that Ethanol E15 will cause trouble.

    Here in Italy, they proved that A20 (alcoholic fuel with a mixture of M15 Methanol and E5 Ethanol) works just fine in regular vehicles with Petrol (Gasoline) engines.

    So the Americans using E15 Ethanol is perfectly fine. If you see any gas station that sells E15, please stop by an fill your car. That way you reduce the oil consumption by another 5% and also the pollution to some extent.

  5. Go Speed Racer on Sun, 5th May 2019 9:11 pm 

    Like hell. Americans dont want
    your corn gas. We want premium.
    High Octane. With tetra ethyl lead.
    Fill er up!

  6. makati1 on Sun, 5th May 2019 9:28 pm 

    Pete, do you REALLY reduce pollution? Isn’t that just the hype (propaganda) to sell corn?

    If you get less miles per gallon, and have to burn more gallons of….’blend’…., I would bet a months income that the TOTAL pollution per mile driven is the same, or more, when you add in the pollution caused by the growing, refining, transporting and blending in it’s manufacture. You have to also look at the pollution in the pesticides/herbicides, and all other externalties involved. Gullible Americans cannot think. They just drool and believe everything they are told by the MSM.

    It’s fun watching the not so good ship Debt sink while the USMSM plays “America the Beautiful” and the Stock Market Casino rearranges the deck chairs so the serfs are bled dry before the cold water of reality washes over them. GO TRUMP! TRUMP IN 2020!

  7. Goat2055 on Mon, 6th May 2019 12:31 pm 

    The EROI on ethanol is too low. It takes a large input of fertilizers, pesticides and fossil fuels to produce it.

  8. Go Speed Racer on Tue, 7th May 2019 1:22 am 

    Makita, I like your sudden enthusiasm
    for Trump in 2020.
    I thought U were not in a mood for that?
    But hey when the left has got boring
    losers like Pelosi, Warren, Hillary,
    and Sanders in his rocking chair, damn
    that Trump looks good all of a sudden don’t he?

    TRUMP in 2020! 4 more years!
    No more immigrants from shithole countries!
    Grab em by the pussy!
    No more Moozlims on welfare!

    Every backyard filled with old tires,
    and a tirefire in every backyard!

  9. makati1 on Tue, 7th May 2019 2:06 am 

    Go, I have been cheering Trump on because he is taking the US down. That needs to happen before the Cons can start another war. He is doing such a great job of helping the US self destruct that he deserves another four years to complete the job. GO TRUMP! TRUMP IN 2020!

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