Official data, history
Diesel seasonality and regional spread
Using 11 full years (2015 to 2025) of EIA weekly retail prices, the three cheapest months for the U.S. average have been January, February, April and the three dearest September, October, November. The gap between those groups is 5.8 points on a scale where a year averages 100. The regional gap is bigger than the seasonal one: the West Coast has sat well above the U.S. average and the Gulf Coast below it. This is history, not a forecast.
Weekly seriesEIA No. 2 diesel retail, weeklyData period: weeks to Oct 5, 2026; seasonal index uses 2015 to 2025Retrieved Oct 9, 2026, 11:03 UTCretrieved Oct 9, 2026
Read this first
The seasonal index is the median over 11 years of each month's average price divided by that year's average. Years with shocks (2020 to 2022) are included, which is why the range bars are wide. Seasonality is a tendency, not a promise. Prices are nominal dollars, not adjusted for inflation. EIA publishes diesel only for the U.S., regions and a few places, so regions stand in for states. The newer EIA API v2 needs a key that was not available to this build, so these figures come from the public EIA history files, which carry the same weekly series.
Which months are cheaper?
U.S. average seasonal index by month. Bars above the line are months that were dearer than the year average, bars below were cheaper.
Seasonal index by region and month
Blue cells are cheaper than the year average, orange cells dearer. Every value is printed.
| Region | Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| U.S. | 97.5 | 98.1 | 99.9 | 97.4 | 100.4 | 100.2 | 101.7 | 100.3 | 102.4 | 104.3 | 103.8 | 98.7 |
| New England | 99.2 | 101.0 | 101.1 | 99.5 | 99.7 | 100.6 | 100.8 | 99.1 | 99.9 | 101.2 | 100.8 | 101.0 |
| Central Atlantic | 98.8 | 99.4 | 99.7 | 98.5 | 99.8 | 100.3 | 101.0 | 99.4 | 100.4 | 103.3 | 101.7 | 100.2 |
| Lower Atlantic | 98.5 | 98.7 | 100.6 | 97.6 | 101.0 | 100.3 | 101.3 | 99.3 | 101.3 | 102.7 | 103.5 | 99.1 |
| Midwest | 97.3 | 97.8 | 98.6 | 96.8 | 100.7 | 100.7 | 101.6 | 101.0 | 102.7 | 106.4 | 104.0 | 98.6 |
| Gulf Coast | 99.2 | 99.4 | 101.1 | 98.3 | 100.1 | 100.2 | 101.5 | 100.3 | 102.0 | 104.1 | 102.8 | 98.4 |
| Rocky Mountain | 96.0 | 94.9 | 96.9 | 97.4 | 100.3 | 100.2 | 103.6 | 100.5 | 103.8 | 104.2 | 104.9 | 99.7 |
| West Coast | 96.1 | 96.7 | 97.2 | 97.7 | 99.6 | 99.9 | 101.8 | 100.4 | 102.9 | 103.8 | 103.5 | 99.3 |
| California | 95.7 | 96.2 | 98.2 | 97.4 | 99.3 | 99.9 | 100.9 | 100.9 | 102.3 | 103.1 | 102.6 | 99.3 |
Median over 11 full calendar years, 2015 to 2025. A month needs at least 3 weekly prices to count. Source file: data/eia_diesel_history.json.
How far each region sits from the U.S. average
Map shades each state by its PADD region (EIA publishes regions, not states). Click a state or a row.
- -0.30 to -0.30 (1 region)
- -0.07 to +0.02 (3 regions)
- +0.23 to +0.27 (2 regions)
- +0.66 to +0.66 (1 region)
| Region | Latest week $/gal | Average gap 2021 to 2025, $/gal | Latest week gap, $/gal | Cheapest 3 months | Dearest 3 months | Dearest minus cheapest, index points |
|---|---|---|---|---|---|---|
| U.S. | $6.199 | 0.00 | 0.00 | Jan, Feb, Apr | Sep, Oct, Nov | 5.8 |
| New England | $6.476 | +0.23 | +0.28 | Jan, Apr, Aug | Mar, Oct, Dec | 1.8 |
| Central Atlantic | $6.485 | +0.27 | +0.29 | Jan, Apr, Aug | Jul, Oct, Nov | 3.1 |
| Lower Atlantic | $5.699 | -0.06 | -0.50 | Jan, Feb, Apr | Jul, Oct, Nov | 4.2 |
| Midwest | $6.286 | -0.07 | +0.09 | Jan, Feb, Apr | Sep, Oct, Nov | 7.1 |
| Gulf Coast | $5.819 | -0.30 | -0.38 | Jan, Apr, Dec | Sep, Oct, Nov | 4.4 |
| Rocky Mountain | $6.267 | +0.02 | +0.07 | Jan, Feb, Mar | Sep, Oct, Nov | 8.3 |
| West Coast | $7.229 | +0.66 | +1.03 | Jan, Feb, Mar | Sep, Oct, Nov | 6.7 |
| California | $8.082 | +1.08 | +1.88 | Jan, Feb, Apr | Sep, Oct, Nov | 6.2 |
Gap = regional annual average minus U.S. annual average, in dollars a gallon, for each of 2021 to 2025, then averaged. Latest week is Oct 5, 2026. Click a row or a state; rows for regions mark their PADD code.
The spread over 20 years
Annual average gap to the U.S. average in dollars a gallon, four regions. Above zero = dearer than the U.S.
Values come from data/eia_diesel_history.json. California is part of the West Coast region and is always higher than the region as a whole.
What this number means
- Season is a smaller effect than place. The U.S. seasonal swing is 5.8 points, about 6 cents on every $1 of price. The West Coast gap to the U.S. average was +0.66 dollars a gallon on average over 2021 to 2025.
- The cheapest months in this history are not a rule. In some years the pattern flips, which is why the range bars matter.
- Regional averages hide corridors. A route through two regions pays a blend. Pump prices vary within a region by station and by card.
- These are retail pump prices. Your fuel card, bulk tank or fleet discount makes your price different.
What to do about it
- 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 the fuel stops across regions: buy more in the cheaper region when the route allows it, and the calculator below shows the size of that difference.
- Do not hold fuel to chase a month. 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, your card or stops are the problem, not the season.
What fuel timing and place are worth to you
Pick the region where you buy most of your fuel and enter your own gallons.
Gain if flexible gallons were bought in the 3 cheapest months
enter numbers
- Price used
- Typical index in that month
- Cheapest 3 months
- Dearest 3 months
- Extra cost if bought in the 3 dearest
- Gap of this region to the U.S., latest week
- That gap on all your gallons
Formula: gallons x flexible share x price x (100 - average index of the 3 cheapest months) / 100. A past pattern, not a forecast. The example numbers are invented placeholders. Replace them with yours.
Where the numbers come from
Related: freight season planner, diesel price shock pilot.
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