MileCFO
+1 (984) 789-5979 Free audit

Fuel and costs

Diesel Seasonality: Is Season or Place the Bigger Price Effect?

What 11 years of EIA weekly diesel prices say about cheap and dear months, and why the region you fuel in matters more than the month.

4 min read

Fuel pump with a display, a hose and a falling price arrow

Diesel is a large and visible cost, so it is tempting to look for a cheap month. The history says there is a pattern, but it is small, and where you buy is a bigger lever than when you buy. All numbers below come from EIA weekly retail diesel prices. This is history, not a forecast.

How the index is built

The seasonal index is the median over 11 full years (2015 to 2025) of each month's average price divided by that year's average, so a year averages 100. Years with shocks (2020 to 2022) are included, which is why a month can flip in some years. Prices are nominal dollars, not adjusted for inflation. Source: EIA weekly retail diesel history, weeks to Oct 5, 2026, retrieved Oct 9, 2026.

The monthly pattern

For the U.S. average, the three cheapest months have been January, February and April, and the three dearest September, October and November. The gap between those groups is 5.8 index points, about 6 cents on every $1 of price. The typical month ranged from 97.4 to 104.3.

U.S. diesel seasonal index by monthBars for each month show the median index over 2015 to 2025, where a year averages 100. January 97.5, February 98.1, March 99.9, April 97.4, May 100.4, June 100.2, July 101.7, August 100.3, September 102.4, October 104.3, November 103.8, December 98.7. 100 = year average 97.5Jan 98.1Feb 99.9Mar 97.4Apr 100.4May 100.2Jun 101.7Jul 100.3Aug 102.4Sep 104.3Oct 103.8Nov 98.7Dec cheaper than the year averagedearer than the year average
U.S. seasonal index by month, median of 2015 to 2025, year average = 100. Every value is printed on its bar.
U.S. diesel seasonal index by month (year average = 100)
MonthIndexAgainst the year average
January97.5Cheaper
February98.1Cheaper
March99.9Cheaper
April97.4Cheaper
May100.4Dearer
June100.2Dearer
July101.7Dearer
August100.3Dearer
September102.4Dearer
October104.3Dearer
November103.8Dearer
December98.7Cheaper

Source: EIA weekly retail diesel history, U.S. average, 2015 to 2025 median.

Place beats season

EIA publishes diesel prices for the U.S., regions and a few places, not for every state, so regions stand in for states. The gap column below is the regional annual average minus the U.S. annual average, in dollars a gallon, for each year from 2021 to 2025, then averaged.

Regional diesel price versus the U.S. average
RegionLatest week, $/galAverage gap 2021 to 2025, $/galCheapest 3 monthsDearest 3 months
U.S.$6.1990.00Jan, Feb, AprSep, Oct, Nov
New England$6.476+0.23Jan, Apr, AugMar, Oct, Dec
Central Atlantic$6.485+0.27Jan, Apr, AugJul, Oct, Nov
Lower Atlantic$5.699-0.06Jan, Feb, AprJul, Oct, Nov
Midwest$6.286-0.07Jan, Feb, AprSep, Oct, Nov
Gulf Coast$5.819-0.30Jan, Apr, DecSep, Oct, Nov
Rocky Mountain$6.267+0.02Jan, Feb, MarSep, Oct, Nov
West Coast$7.229+0.66Jan, Feb, MarSep, Oct, Nov
California$8.082+1.08Jan, Feb, AprSep, Oct, Nov

Latest week is Oct 5, 2026. Source: EIA weekly retail diesel history. The page diesel seasonality keeps the current figures.

The West Coast has sat about 66 cents a gallon above the U.S. average over 2021 to 2025, and the Gulf Coast about 30 cents below it. Both gaps are far larger, in dollars, than the roughly 6 cents of seasonal swing.

What a small fleet can do with this

  • Look at how much of your fuel you can time. A bulk tank or a fleet account lets you fill more in a cheaper week. Pump-by-pump fill-ups on the road cannot.
  • Plan fuel stops across regions. Buying more in the cheaper region, when the route allows it, is worth more than waiting for a month.
  • Do not hold fuel to chase a month. The cheapest months are a tendency, not a rule, and in some years the pattern flips. Use this to sanity-check a budget, not to time the market.
  • Compare your actual average price per gallon with the regional average each month. If you are above it, your card or your stops are the problem, not the season.

What this does not tell you

  • These are retail pump prices. Your fuel card, bulk tank or fleet discount makes your price different.
  • Regional averages hide corridors. A route through two regions pays a blend, and prices vary within a region by station and by card.
  • Nominal prices over 11 years include inflation, which the index does not remove.

To see what a price move does to your own costs, try the diesel sensitivity tool, and read how a fuel surcharge is meant to cover the swings.

Related guides and tools