The U.S. Energy Information Administration’s weekly diesel price report for May 12, 2026 put the national average on-highway diesel price at $3.51 per gallon — down from the $3.78 average that prevailed through most of Q4 2025. That 27-cent drop sounds like good news for carriers. In theory, lower fuel costs should expand margins. In practice, for a significant number of small carriers, the opposite is happening. Their fuel surcharge revenue is falling faster than their actual fuel spending, because the FSC tables built into their broker contracts and spot rate agreements are not designed to protect carrier economics. They are designed to protect shipper economics.

The fuel surcharge has always been a contested element of carrier economics, but the disconnect becomes most damaging during transitions — when prices are moving in one direction and the FSC tables are calibrated to a base rate established in a different price environment. In May 2026, that transition is happening at a moment when most small carriers are already operating on thin margins due to the extended freight recession, rising insurance costs, and a driver market that is tightening. Getting the FSC structure right is not a secondary concern. It is a core margin protection strategy.

This article explains the mechanics of how FSC tables work, why the standard broker FSC structure systematically undercompensates carriers at current diesel prices, and how to build a FSC formula that is actually tied to your operation’s real fuel cost per mile.

How Broker FSC Tables Are Built — And Why They’re Wrong For Your Operation

The standard broker fuel surcharge table is built around a simple structure: a base diesel price, a baseline fuel efficiency assumption (typically 6.0 to 6.5 miles per gallon), and a cents-per-mile increment that increases as the posted EIA weekly diesel price rises above the base. A typical table might set the base at $2.50 per gallon and add 1 cent per mile for every 6-cent rise in the weekly diesel average above that base. At $3.51 per gallon, that formula would produce a fuel surcharge of roughly 16.8 cents per mile.

The problem is the 6.5 MPG assumption. The American Transportation Research Institute’s annual operational cost report shows that actual average fuel efficiency across the Class 8 fleet in 2025 was 6.2 MPG for newer trucks and as low as 5.4 to 5.7 MPG for older equipment common among small carriers. If your actual fuel efficiency is 5.7 MPG, the true cost of fuel at $3.51 per gallon is 61.6 cents per mile. A broker FSC table built on a 6.5 MPG assumption returns only 54.0 cents per mile in gross fuel cost coverage at the same price — a gap of nearly 7.6 cents per mile that comes straight out of your operating margin on every loaded mile.

That gap compounds across an entire year of operations. On a 100,000-mile annual operation, 7.6 cents per mile in chronic FSC undercompensation represents $7,600 per truck per year in margin leakage — on a cost item that the shipper agreed to bear. The shipper thinks they’re paying for your fuel. They’re not. Their table is paying for fuel at an efficiency your truck does not achieve.

What Diesel Actually Costs Per Mile In Your Fleet Right Now

The first step in building a better FSC formula is knowing your actual fuel cost per mile — not a fleet average, but your specific operation’s number based on your trucks, your lanes, and your actual fuel efficiency. The formula is straightforward: divide your current average diesel purchase price (what you’re actually paying at the pump after any fuel card discounts) by your actual MPG. The result is your fuel cost per mile.

For a carrier purchasing diesel at $3.45 per gallon (after fuel card discounts) with actual fleet-average efficiency of 5.9 MPG, the fuel cost per mile is 58.5 cents. That is the number that needs to be recovered through the FSC. Many carriers do not know this number because they have not tracked actual MPG by truck, which means they are unable to identify that a broker’s FSC table is chronically underpaying them on fuel recovery. Run the numbers for each truck in your fleet separately — a truck with a worn-out engine, a heavy spec, or a high-idle profile can easily run at 5.3 to 5.5 MPG, which puts its fuel cost per mile above 63 cents at current prices.

ATRI’s 2025 operational costs report pegged the industry average cost of fuel at 39.2 cents per mile across the broader fleet — but that average includes large fleets with purchasing power that small carriers don’t have, newer equipment running closer to manufacturer fuel efficiency specs, and private fleets that don’t represent for-hire operating conditions. For a small carrier running pre-2020 equipment on spot or short-term contract freight, the real fuel cost per mile is likely 55 to 65 cents at current diesel prices, not 39 cents. Anchoring your FSC calculations to ATRI fleet-average numbers will systematically underestimate your actual costs.

Building A FSC Formula That Protects Your Margin

A carrier-built FSC formula starts with three numbers: your actual MPG, your base diesel price assumption, and a weekly trigger that updates the FSC as the EIA national average moves. The structure should be: take the current EIA weekly price, divide it by your actual MPG, and the result is your fuel cost per mile that week. Subtract whatever base fuel cost per mile you have baked into your linehaul rate to get the FSC increment that needs to be billed on top.

As a practical example: suppose your trucks average 5.8 MPG and your linehaul rate assumes a diesel base of $3.00 per gallon (which would be 51.7 cents per mile in fuel cost). At the current EIA price of $3.51, your actual fuel cost per mile is 60.5 cents — a difference of 8.8 cents per mile. That 8.8 cents per mile is the FSC your contracts should be generating at current diesel prices. If a broker’s standard table is only generating 5 to 6 cents per mile in FSC at $3.51, you are undercharging by nearly 3 cents per mile on every loaded mile — and that difference is coming out of your net margin.

The key to making this formula work in practice is negotiating it explicitly into your direct shipper contracts and being transparent with brokers about why you use your own FSC table rather than their default one. Brokers who are used to dictating FSC terms will push back, but carriers who bring documented cost per mile data to the negotiation are in a stronger position than those who simply accept the standard table. On direct shipper lanes where you have leverage, a carrier-built FSC formula indexed to the EIA weekly average at your actual MPG is entirely reasonable and increasingly common among carriers who have done the math.

The Tariff Wildcard: How Diesel Prices May Move From Here

Diesel prices do not exist in isolation from the broader economic environment, and May 2026 carries significant price uncertainty for fuel. The US-China tariff truce announced May 14, 2026 — reducing tariffs from 145 percent to 30 percent for a 90-day window — has introduced a near-term demand signal for diesel. If Chinese manufacturing resumes at scale and container volumes through West Coast ports recover from their April declines, the resulting freight surge would push up diesel demand alongside freight demand. Higher diesel demand against a relatively flat domestic production posture would push pump prices back up from the current $3.51 average.

The scenario where diesel moves from $3.51 to $3.80 or higher over the next 60 to 90 days is not implausible given the current trade environment. If that happens and you are locked into a broker FSC table with a $2.50 base and a 6.5 MPG efficiency assumption, the rate recovery will lag behind your actual cost increase. The best time to renegotiate FSC structures is before diesel prices move, not after — which is why the current moment, with prices relatively moderate, is the right window to have those conversations with shippers and brokers.

Empty Miles Are The Hidden Multiplier In FSC Math

One element of fuel cost that FSC tables never address is the empty miles problem. A carrier running 15 percent empty miles — meaning 15 cents of every revenue dollar in loaded miles is not being earned on a portion of actual miles driven — is effectively spending fuel on movements that generate no FSC recovery at all. The fuel burned on deadhead miles from delivery to next pickup is entirely unrecovered regardless of how well-structured your FSC formula is on the loaded portion.

The practical response to empty miles in FSC math is to build the deadhead recovery into your base linehaul rate rather than relying on FSC to cover a cost it was never designed to address. If you know your lanes generate 12 percent empty miles, add the fuel cost of those miles — at current diesel prices, divided by your MPG — to your base per-mile rate calculation, and use the FSC exclusively for the variable component of fuel cost on loaded miles. This structure is more transparent and ultimately more accurate than trying to build empty mile recovery into a FSC multiplier.

How Total Cost Per Mile Context Changes The FSC Conversation

Fuel is only one component of total operating cost, but it is often the only variable cost that gets its own surcharge line. The context matters because carriers who are negotiating linehaul rates without accounting for other rapidly rising cost components — particularly insurance premiums, which have risen sharply in 2026 as nuclear verdicts reached $31.3 billion — may be winning the FSC negotiation while losing the overall margin picture.

Building a complete cost-per-mile model — fuel, driver pay, insurance, maintenance, and equipment cost — is the only way to know whether a given linehaul rate plus FSC is covering your actual costs. For carriers running used Class 8 equipment in the current market, the maintenance cost line has become a significant variable, particularly for trucks approaching or past 750,000 miles. A truck with higher maintenance cost and lower fuel efficiency has a total cost per mile that a generic FSC table will never fully recover — which is the core argument for carrier-specific, data-driven cost modeling rather than accepting shipper or broker default rate structures.

Practical Steps For May 2026

Start by pulling your fuel receipts for the past 90 days and calculating your actual average MPG per truck. Divide your average pump price by each truck’s actual MPG to get your fleet’s real fuel cost per mile distribution. Compare that number to what the FSC tables in your active contracts are generating at current EIA prices. The gap between those two numbers, multiplied by your annual loaded miles, is your annual FSC leakage — the amount you are failing to recover on fuel that shippers nominally agreed to cover.

Once you have that number, use it as the basis for renegotiating the FSC structure on your most important lanes. Present your actual cost data. Propose a carrier-specific table indexed to the EIA weekly price at your actual fleet MPG. On direct shipper accounts, this is a reasonable ask — shippers who want a reliable carrier relationship understand that a partner who is losing money on fuel surcharge math is a partner who will eventually either exit the lane or cut service quality to compensate. On broker lanes where you have less leverage, at minimum get the standard table’s efficiency assumption raised from 6.5 MPG to something closer to your actual fleet number, and negotiate the base price up to match current market conditions rather than a base set in 2022 or 2023.

Bottom Line

The EIA national average on-highway diesel at $3.51 in May 2026 is not a particularly high fuel environment by recent historical standards. But for small carriers operating older equipment on broker FSC tables built around outdated efficiency assumptions and low base prices, the current environment is quietly draining margin on every loaded mile. The fix is not complicated: know your actual fuel cost per mile by truck, quantify the gap between that number and what your FSC tables are recovering, and renegotiate the structure using your real data. With diesel price uncertainty rising ahead of the tariff truce demand pulse, the window to fix this before prices move higher is right now.

Innovative Logistics Group