Inflation is 3.4%. Your tank is up 39%.

The Bureau of Labor Statistics published the August Consumer Price Index on September 11. All items, up 3.4% over the year. Underneath that: shelter up 3.0%, food up 2.7%, the energy index up 16.3%, and gasoline up 27.4%. BLS noted that gasoline alone accounted for over a third of the month's increase in the all-items index.

So one line in the basket is running eight times the headline rate. CPI weights that line at about the share of spending an average household puts into a tank, which is the correct way to build a national statistic and a useless way to budget a household. BLS's Consumer Expenditures report put gasoline and other fuels at $2,694 per household in 2023, roughly 3.5% of total spending, with all of transportation at $13,318 of $78,535, or 17%, in 2024. A retiree who drives four miles to the grocery store and a contractor who puts 400 miles a week on a pickup both read 3.4% in the paper and get nothing like the same bill.

The calculation that matters here is small enough to do standing at the pump. Take the miles you drive in a year, divide by your car's real mpg, multiply by $1.23. That is what the last twelve months added to your fuel cost, and it is the only version of this story that is about you.

Drive 12,000 miles in something that returns 25 mpg and you burn 480 gallons, so the increase runs about $591 a year, or $49 a month. Drive 20,000 miles in a truck that returns 18 mpg and you burn 1,111 gallons, so the identical price move costs about $1,368, or $114 a month. Same national average, more than twice the damage. Neither driver is wrong about what inflation feels like.

Then there is where you fill up. On October 5, AAA had California at $6.3916 and Texas at $3.9052. That is a $2.49 spread between two states on the same day, which is most of a gallon's entire price. The national average is a midpoint between experiences that do not resemble each other, and September was a record month either way: AAA's monthly average came in at $4.33, fifty cents above the previous September record of $3.83 set in 2023.

The Energy Information Administration's weekly survey for the week ending September 28 put regular at $4.465 a gallon, up $1.347 from a year earlier. In the same survey, on-highway diesel came in at $6.382, up $2.628. That is a 70% increase, and almost nobody tracks it, because almost nobody buys diesel.

You pay for it regardless. Freight runs on diesel: the truck restocking the grocery shelf, the rail container, the van that brings the box to your door. Food CPI was up 2.7% in August, well under the headline, which suggests the fuel cost has not finished working its way onto shelves. Surcharges reset on a lag and get folded into shelf prices rather than itemized for you. If grocery inflation picks back up over the next few months, a good part of it started here, and by then it will not look like a gas story at all.

The government's own fuel economy site is refreshingly blunt about the tips you have read a hundred times. Keeping your tires properly inflated improves mileage by 0.6% on average, up to 3% at best, which it prices at about three cents a gallon. Using the motor oil grade your manufacturer recommends is worth 1% to 2%, so four to nine cents. Replacing the air filter on any fuel-injected car, meaning essentially anything built since the early 1980s, does nothing for mileage at all.

The figures that are actually large are all about your right foot. Aggressive driving, hard acceleration and hard braking, costs 15% to 30% on the highway and 10% to 40% in stop-and-go traffic. Every 5 mph above 50 is worth roughly 31 cents a gallon. Idling burns a quarter to a half gallon an hour. Dropping your speed 5 to 10 mph saves 7% to 14%, more than ten times the tire-pressure tip, and it is free.

The expensive mistake here is structural, not behavioral. EIA's September 9 outlook forecasts Brent crude averaging $74 a barrel in 2027, down from $91 in 2026, with retail gasoline at $3.35 a gallon next year against $3.84 this year. Hold that loosely. It was published while traffic through the Strait of Hormuz, which carries roughly a fifth of the world's oil supply in peacetime, was disrupted, and AAA had WTI sitting at $90.42 on October 1. But it is the official forecast, and it argues hard against solving a fuel problem with a seven-year loan. Trading a paid-off car for a more efficient one to save $600 a year of gas is a bad trade if the gas saving shrinks and the payment does not.