1. The short answer
If your tank is below a third, buy now. Between a third and two thirds, split the order. Above two thirds, wait but get your quotes lined up. That is the whole rule. Everything below explains why it is shaped that way and when to break it.
The logic is not a price forecast. It is a risk position. An empty tank in a market where the Strait of Hormuz is running at roughly a tenth of its pre-crisis shipping traffic is a supply problem, not a price problem. A full tank lets you sit out a bad week without consequences.
2. Where prices actually stand
Short answer: the last in-season reading was $5.535 a gallon, and crude has surged since. The EIA's weekly residential heating oil series runs through the heating season and paused for the year at the week ending 30 March 2026: $5.535 per gallon for the US average and $5.583 for the East Coast, both excluding taxes. The next readings arrive when the series resumes in October.
What has moved since then is the crude leg. Brent closed at $103.98 a barrel on 11 September 2026, after touching a weekly high of $107.60, up about 9 percent on the week; by 22 September 2026 it had eased to $99.97 (17:30 UTC, our own data feed). The move follows a Houthi strike on Saudi oil infrastructure on 8 September and the Houthi seizure of the Yemeni Red Sea port of Mokha, near the Bab el-Mandeb strait, on 11 September. Brent traded above $100 a barrel that week, and the Strait of Hormuz remains effectively closed to commercial traffic.
For context on the wider fuel picture: the national average gasoline price reached $4.10 on 20 August 2026, the highest ever recorded for that date, making this the most expensive August on record at the pump. Heating oil and gasoline share the same crude input, so that is the backdrop your dealer is quoting against.
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3. Why the supply picture matters more than the seasonal pattern
Short answer: the usual summer discount is thin this year because the supply side is broken. In a normal year, off-season demand pulls retail prices down and the pre-buy window is where households save. In 2026 that mechanism is competing with a genuine shortage.
The IEA's August report had put numbers on it: Gulf exports, including routes that bypass the Strait of Hormuz, had fallen 2.1 million barrels a day to 15 million, and Gulf production sat 8.3 million barrels a day below pre-war levels. Little has eased since. Shipping data put Hormuz traffic at roughly 12 to 13 tankers a day in early September, against around 100 a day before the crisis, and the IEA's September report, published 11 September 2026, expects the Hormuz restrictions to persist through the rest of the year.
The counterweight is demand destruction, and even that has moved against households this month: the IEA's September report puts the 2026 demand contraction at 2.5 million barrels a day, revised sharply down from the 1.6 million estimate in August and comparable to the four largest demand shocks of the last 60 years. EIA data also show US distillate stocks running 13 percent below their five-year average, with refineries running at 97.8 percent utilization. That combination is why relying on a seasonal discount remains the weakest of your three levers this year.
4. Pre-buy, cap, or variable: what each contract actually does
Pre-buy means paying up front for a fixed number of gallons at today's price. You take the price risk off the table and take on counterparty risk instead - if the dealer fails, your money is exposed. Check whether the contract is bonded or escrowed before signing.
Price cap sets a ceiling but lets you benefit if the market falls. You pay a premium for that asymmetry, typically built into the per-gallon rate. In a market where Brent moved about 9 percent in a single week this September, that premium is worth more than in a calm year.
Variable means you pay the market rate at each delivery. Cheapest if prices fall, most exposed if the Hormuz situation deteriorates. Reasonable only if your tank is full enough that you can time deliveries.
Whatever you sign, get the per-gallon price in writing along with the delivery minimum. Quotes that omit the minimum delivery quantity are not comparable - the same dealer can be cheapest at 300 gallons and mid-pack at 150.
See what $120, $150 or $180 per barrel would cost your household.
Run the scenario5. The decision table
Find the row that matches your tank and follow it. The point of a rule is that it protects you from the daily headline cycle.
- Below one third - order now, full delivery. With Hormuz shipping still running at a fraction of pre-crisis levels, delivery certainty is worth more than the last few cents. Take a cap contract if one is offered at a reasonable premium.
- One third to two thirds - split it. Half now, half in October when the EIA weekly series resumes and you can see actual retail prints again. You average your cost and stay supplied.
- Above two thirds - wait, but prepare. Collect three written quotes now so you can act within a day if the Strait reopens and crude drops.
- Any level - be done before the first hard freeze. Demand spikes and delivery windows stretch as soon as temperatures break.
6. When to break the rule
Break it downward if the Strait reopens. Qatar reported on 12 August 2026 that Oman-Iran talks were at an advanced stage, but Iran's parliament speaker said on 3 September 2026 that Tehran maintains full control of the Strait and will not allow it to reopen, according to Al Jazeera. A reopening remains the single event that would move prices down sharply, but there is no sign of one right now. If you are above two thirds, it is still worth watching for, just do not plan around it.
Break it upward if sanctions bite. On 24 August 2026 the US Treasury announced expanded secondary sanctions under the name Operation Economic Outcast, designating close to 60 entities, individuals and vessels across five sectors. China takes roughly 90 percent of Iran's crude exports; if the sanctions reach Chinese buyers, more supply leaves the market.
Do not break it for a single day's move. Brent fell about 2.5 percent on the day the sanctions were announced, despite the news being supply-restrictive. Daily moves are noise, not signal.