The Weekly Fill-Up | September 1-5

September 2, 2025

As we step into September, energy markets across the United States and here in South Dakota are entering a period of transition. Seasonal demand shifts, global supply dynamics, and regional inventory levels are shaping the outlook for fuel, propane, and DEF. Here’s what you need to know this week.

Fuel & Diesel Markets

Nationally, the U.S. Energy Information Administration (EIA) projects that retail gasoline prices are expected to ease moving into fall, with averages trending toward $2.90 per gallon or lower in 2026. For the remainder of 2025, softening crude oil prices are expected to relieve pressure on gasoline and diesel markets. Diesel remains especially important to South Dakota’s agricultural and transportation sectors, and while inventories remain tight, forward indicators suggest a moderation in costs.

In South Dakota, wholesale and retail diesel prices are reflecting this national trend. Local markets remain sensitive to harvest-season demand, which traditionally increases usage in September. Cooperative members should anticipate moderate price volatility as regional supply balances against heightened agricultural fuel consumption.

Propane Outlook

Propane markets are also adjusting as we transition from summer into the pre-heating season. According to the EIA, wholesale propane in South Dakota was last reported at $0.825 per gallon in May, compared to $0.932 at this time last year. While reporting pauses during the summer months, early September indications suggest propane remains in this range.

On the U.S. level, propane futures for winter 2025–26 are trading near $0.83 per gallon, above the 10-year average of $0.74. This indicates buyers are hedging against potential winter supply risks. Global dynamics are also influencing the market: U.S. propane exports continue to be redirected away from China due to ongoing tariffs, with volumes now flowing more heavily to Europe, Japan, and India. This shift has expanded domestic inventories, helping stabilize local markets despite global uncertainty.

For South Dakota customers, this means current propane pricing remains competitive. However, with winter approaching, now is an ideal time to explore pre-buy or budget programs to lock in supply and manage costs effectively.

DEF (Diesel Exhaust Fluid)

While DEF prices are less widely reported than gasoline or propane, they tend to move alongside diesel markets since urea production and transportation costs are tied to fuel. With diesel prices expected to soften, DEF costs are likely to remain steady or experience slight relief in the coming months. For agricultural fleets, over-the-road trucking, and construction operations, this should provide modest cost stability during a season of heavier usage.

Looking Ahead

Energy markets during the week of September 1–5 are defined by moderation and preparation. Gasoline and diesel are easing off summer highs, propane is stable yet carrying forward-looking premiums, and DEF is holding steady. For Sioux Valley Coop members, this is a critical time to evaluate fuel strategies, confirm propane supply plans, and stay proactive as we move toward the winter heating season.

As always, Sioux Valley Coop is here to help you navigate these shifts—from bulk fuel delivery to propane keep-full programs to DEF availability at our cardtrol and C-store locations. Our mission is to keep you powered locally with reliable energy solutions.

Sources:

U.S. Energy Information Administration (EIA), Short-Term Energy Outlook – eia.gov
EIA Propane Data for South Dakota – eia.gov
South Dakota Wholesale Propane Price, May 2025 – YCharts
LPG Market Trends & Futures – LP Gas Magazine
Global LPG Trade Outlook – Reuters