Most fleet owners know their fuel cost. Almost none know their true all-in cost per mile by truck. Here's the 6-layer calculation that separates profitable fleets from ones bleeding money.
Ask any fleet owner their cost per mile and you'll get one of two answers: a fuel number, or a shrug. The fuel number is wrong because it's incomplete. The shrug is honest but expensive.
True cost per mile isn't one number — it's six layers stacked on top of each other. When you see all six, you understand why some trucks make money and others destroy it while looking identical on a dispatch sheet.
The American Transportation Research Institute (ATRI) publishes the most cited trucking cost benchmark in the industry. Their 2024 number: $2.26 per mile average marginal cost for Class 8 truckload carriers. But that's a fleet-wide average — your worst truck might be running at $2.80 and your best at $1.90. The gap between them is where profit lives or dies.
This is the one everyone knows. Gallons burned times price per gallon, divided by miles driven. A truck averaging 6.5 MPG at $3.85/gallon diesel runs about $0.59/mile in fuel alone.
But here's what most operators miss: idle fuel. A Class 8 truck burns roughly 0.8 gallons per hour at idle. If your driver idles 6 hours a day (not uncommon for sleeper cab operators), that's 4.8 gallons wasted — $18.48/day, $5,500/year per truck — and it never shows up in your MPG calculation because the truck wasn't moving.
This is why telematics data matters. Your ELD (Motive, Samsara, Geotab) knows exactly how many hours each truck idled. Multiply by 0.8 gallons/hour times your average fuel price, and you have your idle waste in dollars — the number nobody in trucking talks about but everybody pays.
Company drivers typically earn $0.45-$0.85 per mile (CPM), owner-operators take 25-30% of linehaul revenue, and local drivers earn $20-$35/hour. Many fleets have all three models running simultaneously.
The calculation seems simple — pay divided by miles — but the financial question is different: which drivers generate the most revenue per dollar of compensation? A driver earning $0.70/mile who runs 2,800 miles/week is cheaper per mile than a driver earning $0.55/mile who only runs 2,000 miles/week when you factor in the fixed costs that accumulate regardless of miles driven.
Primary liability, cargo, physical damage, workers comp. For a small fleet, insurance typically runs $12,000-$18,000 per truck per year. Divide by annual miles (100,000-130,000 for a typical OTR truck) and you get $0.10-$0.18/mile.
Most operators pay this as a monthly or annual premium and never think about it on a per-mile basis. But it's a fixed cost that gets more expensive per mile on every truck that's sitting — a truck that runs 80,000 miles/year instead of 120,000 costs 50% more per mile in insurance alone.
Preventive maintenance, tires, breakdowns, DPF cleaning, brake jobs. ATRI benchmarks this at roughly $0.20/mile, but the variance between trucks is enormous. A 2023 Kenworth T680 at 180K miles might run $0.12/mile in maintenance. A 2019 Peterbilt 389 at 520K miles might run $0.35/mile — nearly 3x.
This is where maintenance records become financial data. If you're tracking repair invoices in a shoebox (or not at all), you can't see which truck crossed the threshold where maintenance cost exceeds the value of keeping it running.
A new Class 8 truck costs $150,000-$180,000. Over a 5-7 year useful life at 120K miles/year, that's roughly $0.18-$0.25/mile in depreciation. Used trucks depreciate faster in the first two years, then flatten.
The financial question isn't just "what did I pay for this truck" — it's "at what mileage does the combination of depreciation, maintenance, and downtime cost more than a new truck payment?" That crossover point is different for every truck and requires seeing layers 4 and 5 together.
Tolls, permits, IFTA fuel tax, truck washes, lumper fees, ELD subscriptions, parking. Individually small, collectively significant. A truck running Northeast corridors with heavy toll roads might add $0.15-$0.20/mile in tolls alone.
Stack all six layers for a typical 5-truck fleet:
Truck Fuel Driver Insur Maint Deprec Other TOTAL CPM T-101 $0.61 $0.42 $0.12 $0.14 $0.20 $0.11 $1.60/mi T-102 $0.73 $0.42 $0.12 $0.18 $0.20 $0.13 $1.78/mi T-103 $0.58 $0.42 $0.12 $0.12 $0.22 $0.10 $1.56/mi T-104 $0.89 $0.42 $0.14 $0.35 $0.18 $0.15 $2.13/mi ← Problem truck T-105 $0.60 $0.42 $0.12 $0.15 $0.22 $0.11 $1.62/mi Fleet avg: $1.74/mi
T-104 costs $0.53/mile more than the fleet average. On a truck running 10,000 miles/month, that's $5,300/month in excess cost — $63,600/year. That's not a maintenance problem or a fuel problem. It's a financial visibility problem. Nobody told the owner because nobody calculated it.
The data exists. Your ELD has miles and idle hours. Your fuel card has gallons and dollars. Your accounting system has insurance, loan payments, and repair invoices. Your payroll has driver compensation.
The problem is these live in six different systems that don't talk to each other. Motive doesn't know what you paid for fuel. QuickBooks doesn't know which truck burned it. Your fuel card doesn't know the truck's mileage. So fleet owners do one of two things: build a massive spreadsheet that takes hours to update (and is always out of date), or accept that they don't know their true cost per mile by truck.
Neither option is acceptable when your industry runs on 3-6% net margins. At those margins, the difference between a profitable truck and a money-losing truck is invisible without this calculation — and the difference between knowing and not knowing is the difference between a fleet that grows and one that quietly bleeds.
Start with what you have. If you use Motive or Samsara, you already have miles, idle hours, and fuel consumption per truck. Multiply idle hours by 0.8 gallons by your average diesel price — that's your idle waste in dollars. It's the fastest win because it requires zero additional data sources.
Then layer in your fuel card data (actual dollars per gallon per truck), your insurance (annual premium divided by miles), and your maintenance invoices (by truck, by year). Each layer you add makes the picture sharper.
The goal isn't perfect precision — it's financial visibility. When you can see that T-104 costs $0.53/mile more than your fleet average, you can act on it. Without the number, you're guessing.
OperatorIQ connects to your Motive or Samsara ELD and calculates cost per mile by truck automatically — fuel CPM from telematics, idle waste in dollars, and fleet health scores. No spreadsheets. See what it looks like with a 5-truck fleet demo →
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