Methodology & Specifications

Abridged Edition | Weaver (Version 1.0) | July 2026

Mills Price, LLC (“Mills”) publishes price benchmarks for United States refined fuels, gasoline and diesel, sold at the spot market and wholesale rack market level, together with complementary data such as fuel logistics costs. This page covers the essential elements of the Mills methodology: what Mills prices are, how they are assessed, what they cover, when they publish, and how to reference them in a fuel supply contract.

This is the abridged edition. The complete Methodology & Specifications Guide, including the full assessment directories, complete specification detail, logistics route and fee tables, and worked pricing examples, is available to registered users: sign up or log in.

Two Prices, One System

Mills publishes two related price families: the Mills Assessed Rack Clearing (MARC) Price and the Mills Efficient Market Estimate (MEME) Price. A MARC Price is an assessment of what the market did; a MEME Price is an estimate of what the market should be given the wider price structure.

The two are mutually reinforcing. The MEME Price gives every rack terminal city a defensible expected value, computed the same way everywhere and at every moment, against which the bids, offers, and trades behind MARC Prices are validated. It also fills and stabilizes prices in thinly traded markets where a true MARC Price cannot be published, so pricing coverage is continuous rather than gapped.

The MARC Price

The MARC Price is Mills’ flagship rack price benchmark: a price assessment of a transactable, market-clearing price for a given specification of wholesale fuel, at a geographic location, at a specific time. It is intended for use as the price basis in rack-level or dealer tank wagon (DTW) fuel supply contracts, and in day-deal transactions, in the same way existing price indexes such as OPIS or DTN are used today.

Different: methodology. A MARC Price is an editorial price assessment, not a statistical low or average of posted rack prices. It combines actuals (executed trades, firm bids, and firm offers) with the MEME Price estimate to determine the point at which a willing buyer and a willing seller would actually transact.

Why that matters. Many rack contracts reference the low or average of posted prices at a terminal city. That approach is exposed to distortion: a supplier that posts an artificially low price may sell little or no volume at it, yet every contract tied to that low is affected. For wholesalers and jobbers this compresses sell-side margins and creates basis risk against spot-level buy-side positions. Mills applies the same assessment-based approach the industry already trusts in upstream spot markets, a proven method for eliminating such distortions.

Similar: everything you already reference. MARC Prices publish at the rack terminal city granularity, on a gross volume basis (the physical gallons that cross the rack meter at observed temperature), for gasoline, diesel, and associated biofuels aligned with the relevant ASTM and API standards.

Price Input Hierarchy

MARC Prices rely on four ranked inputs: concluded transactions first, then firm bids and offers, then derived market information. Higher-ranked inputs govern; lower-ranked inputs fill in and stabilize. Where a higher-ranked actual contradicts the MEME estimate by more than the location’s tolerance, it is flagged in real time and a human assessor confirms it against corroborating market evidence before it can move the assessment.

The MEME Price and the Weaver Pricing Engine

The MEME Price is a baseline price estimate with two jobs: it gauges the market representativeness of the bids, offers, and trades reported to Mills, letting the price desk identify outlier or falsely reported prices quickly, and it serves as the foundational layer of the assessment itself. In thinly traded markets, Mills may publish a MEME Price in lieu of a MARC Price. That substitution is the methodology’s standing thin-market contingency, disclosed in advance: when transactional evidence is absent, the published value is a derived estimate, not an improvised judgment.

MEME Prices are calculated by Mills’ proprietary Weaver Pricing Engine, which applies a fully auditable stack of named, additive adjustments to root futures and spot market prices, weaving the price signal into downstream rack markets. Each adjustment draws on published, verifiable inputs (exchange settlements, carrier tariffs, and regulatory and pipeline RVP calendars) or on stated historical derivations, so a given day’s inputs reproduce the same MEME Price on recalculation. There are six classifications of adjustment, applied in order:

1. Futures curve: the carry premium or discount implied by contango or backwardation.
2. Logistics: the cost to move and handle product between two points, built from operator-published pipeline tariffs, line-loss allowances, terminal throughput fees, freight rates, and related fees.
3. Regulatory zoning: the premium or discount between regulatory fuel grades, such as conventional versus reformulated gasoline (RFG), or standard versus low-emission diesel.
4. Seasonality: the premium or discount between seasonal specifications, principally Reid vapor pressure (RVP, a measure of gasoline volatility) for gasoline and winterization for diesel.
5. Grade / octane: the premium or discount across octane ratings and ethanol or biodiesel blend levels.
6. Fundamentals: local supply and demand effects not captured above, applied as a historically derived residual and refreshed approximately weekly.

The complete guide walks the full engine end to end: a 19-step worked example carrying a NYMEX futures price through the spot markets and into a finished, published rack price at Birmingham, AL.

Reading a Mills Price Code

Every published price carries a unique alphanumeric code. A core code identifies the product at a place: a three-character location prefix, a product suffix, and an optional dash-separated RVP band for gasoline. Two parenthesized positions qualify each published print: a time stamp and a price type. The worked symbol below decodes a Houston rack price, read left to right:

Worked symbol: TXHGR87-A(TR)(c), the Houston, TX RFG 87 E10 rack price at 9.0 psi, struck at the 10:00 a.m. ET rack contract time, published as a contract benchmark.

Spot basis codes begin with X (a regional spot market rather than a terminal gate): XGHCC87-A(TS)(c) is the Gulf Coast (Houston) spot price for CBOB 87 blendstock at 9.0 psi, struck at the 3:30 p.m. ET spot close. The complete guide decodes every position and RVP band in full.

Product Codes

The product suffix comes from three code families. Position 4 is the product class: G finished gasoline, R RFG blendstock, C conventional blendstock, U unblended (ethanol-free) gasoline, D diesel/distillate, E ethanol. Position 5 is the subclass, the regulatory regime or RIN status. A blendstock is sub-octane base gasoline before ethanol is added (RBOB for reformulated markets, CBOB for conventional); finished E10 is blendstock plus 10 percent ethanol, splash-blended at the rack.

Gasoline

Diesel

Ethanol and Renewable Credits

Reading a Mills Logistics Code

Fuel logistics costs carry their own code family, prefixed Q. Every transport leg decomposes into edges (the line-haul itself: the carrier tariff plus its loss allowance) and nodes (the terminal handling at each end: the inbound pump-over, any blending or additive service, and the outbound truck-rack loading). A leg code is positional and reads Q[type][fee][fuel]:[origin]>[destination]([operator]); a terminal-node code drops the route, so QMT is the truck-rack loading node. The worked symbol below decodes a Colonial Pipeline leg, read left to right:

Worked symbol: QPFG:TXH>ALB(CPL), the Colonial Pipeline line-haul tariff for gasoline shipped from Houston, TX to Birmingham, AL.

Logistics rates are looked up live per route and terminal at the moment of pricing rather than published as static tables. The complete guide documents the full code structure: the pipeline, rail, and barge route registry, the terminaling fee families, and the operator codes.

Coverage

The current Weaver (Version 1.0) publishes:

• 1,116 rack assessments across 101 rack terminal cities, listed by PADD and state, each cross-referenced to its OPIS terminal city code and regulatory regime.
• 59 spot assessments across 8 spot markets: New York Harbor, New Jersey, Macungie PA, Gulf Coast (Houston), Gulf Coast (Dallas/Ft. Worth), Chicago, Group 3 (Tulsa), and Group 3 (Denver).
• Fuel logistics assessments covering pipeline tariffs, line-loss allowances, terminal throughput fees, and rail freight, each carrying its own auditable code.

Products covered: finished E10 gasoline (regular, midgrade, and premium, in conventional and RFG grades), gasoline blendstocks (CBOB and RBOB), ethanol-free clear gasoline (E0), ultra-low-sulfur diesel (clear, dyed, and Texas Low Emission Diesel), denatured fuel ethanol (with RIN), and the D6 RIN renewable credit. Specifications are regime-aware: each terminal city posts the grades its regulatory zone actually requires.

Publication Schedule

Rack prices publish twice daily on each business day that U.S. petroleum spot markets are active, following the NYMEX trading calendar. Spot benchmarks publish daily at the spot close.

The final position of every symbol is the price type: what kind of price the print is. The contract benchmark (c) is the print to reference in supply contracts; the bid, ask, and trade prints record the direct market evidence behind it:

Statistical low, high, and mean prints (l, h, m) are also published for each window.

Specifications at a Glance

How to Use Mills Prices in Contracts

Mills prices are designed as the pricing basis for physical wholesale purchase contracts at the rack (day deals and term deals). They are assessments of the market-clearing level at a point in time, not guaranteed transaction prices. To reference one, a contract names the product at a rack terminal city and pins it to a Mills price code carrying the contract benchmark price type (c) at the morning rack time (TR) or evening rack time (TE). The excerpts below are copy-pastable examples.

Supply Contract Example

Alternative: RVP Specified (Mills Price Code Position 8)

Alternative: Spot-Linked Supply Contract

Rack-delivered supply deals are sometimes priced off the upstream spot benchmarks instead of the local rack benchmark: the contract references the source blendstock and ethanol spot prices plus an adder covering everything between the spot hub and the rack. Mills logistics codes let the parties write that adder as named, auditable components rather than a single opaque number. The example below mirrors the Weaver derivation of the same product in the complete guide: 90 percent US Gulf Coast CBOB 93, 10 percent Chicago ethanol, plus the delivery legs into Birmingham, AL.

Assessment Integrity

Independence. Mills is a price reporting organization, not a market participant: it does not trade, broker, or hold title to the fuels it assesses, and it has no financial interest in the level at which any assessment publishes.

Data quality. Bids, offers, and trades are accepted from identified market participants and screened before they can influence an assessment: checked for staleness and off-market levels, monitored for selective-reporting patterns, and reviewed where one reporting entity accounts for a disproportionate share of the evidence behind a location. Exclusions are logged with their reasons.

Corrections. If a published price is found to be in error, Mills corrects it, identifies the corrected print as a correction, and retains both the original and corrected values in the assessment record.

Methodology changes. Material changes are announced ahead of their effective date and recorded in the guide’s revision history, so a contract referencing a Mills price can always identify the edition that governed a given pricing day.

Mills prices are assessments of market-clearing levels at a point in time and should not be construed as guaranteed transaction prices. Actual transaction prices may differ due to counterparty-specific terms, credit conditions, volume commitments, or delivery logistics. Mills prices do not include branded product premiums.

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