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A 20-truck fleet manager in Nashville is running the numbers on whether to hire a diesel technician and lease shop space. The math on paper looks straightforward: a technician at $65,000 per year, a bay at $3,500 per month, some tools. Maybe $110,000 annually all in. The fleet spends $316,000 per year on repair and maintenance at current rates. Bringing work in-house should cut costs significantly.
The actual number, once every cost category is included, is closer to $185,000 to $220,000 annually for a single-technician, single-bay operation. That gap between the estimate and the reality is where the in-house decision breaks down for most fleets in the 10 to 50 truck range, because the costs that are easy to undercount add up to more than the labor rate savings that made the idea attractive.
In-house operations carry substantial overhead beyond technician wages: facilities, equipment depreciation, training, and compliance can add 40 to 60% to direct labor costs. For a fleet manager comparing hourly rates on paper, this is the multiplier that makes the in-house calculation look better than it is. The $29 per hour technician does not cost $29 per hour. They cost $29 per hour plus everything else.
Here is what everything else actually includes for a fleet building its first in-house shop.
Technician compensation. The Bureau of Labor Statistics puts the median annual wage for diesel service technicians and mechanics at $60,640 as of May 2024. Fullbay's State of Heavy-Duty Repair puts the median hourly rate for 2025 at $33 per hour, a 10% year-over-year increase from the $30 per hour rate in 2024. For a fleet hiring a qualified technician with Class 8 experience and diagnostic capability, the realistic salary range is $65,000 to $80,000 depending on market and experience level. Senior technicians with 8 to 15 years of experience command $62,000 to $79,000, and master technicians with diagnostics and electronics expertise regularly exceed $85,000.
That salary is the starting number, not the total. Benefits add 25 to 35% to base compensation in commercial fleet environments: health insurance, employer-side payroll taxes (7.65%), retirement contributions, paid time off, and workers compensation. On a $70,000 salary, fully-loaded compensation including benefits and taxes runs approximately $88,000 to $95,000 annually.
Facility cost. Leasing commercial bays for heavy-duty vehicles runs $2,000 to $4,500 monthly in most markets. A bay sized appropriately for Class 8 work needs to accommodate a full tractor-trailer, meaning 60 to 70 feet of depth with appropriate door height. Commercial property suitable for heavy-duty vehicle repairs typically costs $8 to $15 per square foot annually in most markets, with a 10,000 square foot facility running $6,500 to $12,500 per month. A single-bay operation sized for Class 8 work in most non-coastal markets runs $3,000 to $5,000 per month including base rent, CAM charges, and utilities. Annual facility cost: $36,000 to $60,000.
Diagnostic equipment. A well-equipped heavy-duty shop maintains scan tools from multiple OEM platforms including Cummins Insite, Detroit Diesel Diagnostic Link, and PACCAR Davie, each requiring licensing fees and annual updates. Diagnostic equipment investment alone can exceed $50,000 for comprehensive coverage. For a 20-truck fleet running two or three OEMs, the minimum credible diagnostic investment includes platform-specific software licenses, a quality multi-platform scan tool, and OEM-specific hardware adapters. The entry-level cost for this capability is $25,000 to $40,000, with annual software update and licensing fees running $3,000 to $8,000 on top. Heavy-duty lifts capable of supporting a loaded Class 8 vehicle add another $15,000 to $35,000 depending on configuration.
This equipment does not depreciate slowly. Diagnostic software requires active license maintenance, and OEM updates that are not purchased mean the technician cannot correctly diagnose problems on current-year trucks. A shop that skips two years of updates on Cummins Insite is not a credible diagnostic resource for newer Cummins-powered trucks.
Tools and consumables. Beyond the capital diagnostic investment, a technician's tool inventory represents a meaningful ongoing cost. Professional-grade hand tools, specialized air brake service equipment, torque wrenches calibrated for Class 8 fasteners, and emission system service tools collectively represent $15,000 to $30,000 in initial investment and $3,000 to $5,000 in annual replacement and addition. Shop supplies, waste disposal, and lubricants add another $6,000 to $12,000 annually at one-bay utilization.
Training and certification. Ongoing technician education, certification maintenance, and skill development are critical for maintaining service quality and adapting to new equipment technologies. ASE certifications for heavy-duty trucks require periodic renewal. OEM-specific training courses for aftertreatment, electrical systems, and advanced diagnostics run $500 to $2,000 per course, and a technician needs two to four per year to stay current on modern Class 8 systems. Annual training budget: $2,000 to $6,000.
Insurance and compliance. A commercial shop operation requires garage liability insurance ($3,000 to $8,000 per year), workers compensation at fleet maintenance rates, and environmental compliance coverage for waste oil and fluid handling. Total insurance overhead: $5,000 to $12,000 annually.
Adding the realistic ranges for each category produces the actual annual cost of a single-technician, single-bay in-house maintenance operation for a 10 to 50 truck fleet:
Technician total compensation: $88,000 to $95,000 Facility (bay lease plus utilities): $36,000 to $60,000 Diagnostic equipment (amortized over 5 years plus annual licenses): $14,000 to $22,000 Tools and consumables: $9,000 to $17,000 Training and certification: $2,000 to $6,000 Insurance and compliance: $5,000 to $12,000
Total annual overhead: $154,000 to $212,000
That is the fixed cost of maintaining the in-house capability before a single repair event is completed. The fleet still pays for parts on every repair. It still pays for any work that exceeds the single technician's capacity or capability, which includes complex engine work, transmission overhauls, and aftertreatment repairs requiring dealer-level tooling that most in-house shops do not carry.
This fixed cost needs to be recovered through labor savings on repairs that would otherwise go to outside shops. LTL carriers doing 78% of maintenance in-house pay $45 to $75 per hour in labor, while fleets outsourcing the same work pay $125 to $175 per hour. On a 20-truck fleet spending $316,800 annually in R&M with labor accounting for approximately 40% of that spend, the labor portion is around $126,720. Recovering that labor at in-house rates ($45 to $75 per hour) versus market rates ($125 to $175 per hour) represents a theoretical maximum saving of roughly $63,000 to $84,000 per year, assuming the in-house technician handles all of it.
Against a fixed overhead of $154,000 to $212,000, a labor saving of $63,000 to $84,000 does not cover the overhead. The in-house operation costs more than the savings it generates at the 20-truck fleet scale for a standard R&M spending profile.
The in-house model becomes financially viable when three conditions are met simultaneously. Fleet size is large enough that a single technician is running at near-full capacity, meaning 40-plus trucks with a consistent maintenance volume. The fleet operates from a centralized location where trucks return regularly rather than running multi-state dispersed routes. And the fleet's work order profile is dominated by high-frequency, lower-complexity work that an in-house technician handles efficiently, rather than complex OEM-specific diagnostic work that requires capital equipment not worth purchasing for low volumes.
The most important operational insight from fleet maintenance cost research is that the planned-versus-unplanned gap, at roughly 7 times cost difference, dwarfs the in-house-versus-outsource gap at approximately 1.5 times. A fleet that builds an in-house shop but runs at 70% PM compliance will spend more than a fleet that outsources but runs at 94% PM compliance. The shop does not fix the planning problem. It just changes where the labor cost occurs.
For fleets operating across multiple states, the in-house model has a structural limitation that cost math alone does not capture: the technician is where they are. When a truck breaks down in Colorado and the shop is in Memphis, the in-house capability is irrelevant. The fleet is paying for a shop in Memphis and calling a walk-in shop in Colorado. The fleet PM tracking article covers the interval execution problem that multi-state fleets face regardless of whether they have in-house capability, because the problem is geographic, not mechanical.
The coordination cost article on this site covers the full math on what a coordination program costs a 20-truck fleet annually. The short version: using the published service fee structure on 60 managed repair events per year at an average invoice of $2,500, the annual fee runs approximately $10,740. Pre-negotiated network pricing recovers 15 to 25% on labor and parts across those events, producing gross savings of approximately $30,000 against that fee. Net saving: $19,260 for that portion of managed spend.
Against a fixed in-house overhead of $154,000 to $212,000 annually, the coordination program's annual fee for the same fleet is not a comparable cost. It is a fraction of the overhead the in-house shop would generate regardless of repair volume.
The comparison that actually produces a useful answer for a 10 to 50 truck fleet is not in-house cost versus outsource cost in the abstract. It is the total fully-loaded in-house cost including all overhead versus the total coordination program cost including service fees, at the fleet's actual repair volume and geographic distribution. For most fleets in this size range running across multiple states, that comparison does not favor the in-house shop.
If you want to understand what your fleet's specific preventive maintenance and repair profile looks like in terms of coordination program cost versus the in-house overhead the same volume of work would require, the fleet maintenance plans page covers the fee structure in detail. For a specific calculation against your fleet's actual invoice history and operating footprint, reach out through the contact page. The comparison is more useful with real numbers than with industry averages.
This article draws on the following sources:
