What Happens to the Value of a Semi-Truck After 500,000 Miles?

A semi-truck doesn't suddenly lose value when the odometer hits 500,000 miles, but mileage increasingly becomes part of the equation. Buyers start paying closer attention to engine hours, maintenance history, major repairs, emissions systems, tires, transmission condition, and how the truck was used. At the same time, the cost of keeping an aging truck on the road can begin climbing. Kelly Truck Buyers purchases used semi-trucks in virtually any condition, but understanding how mileage affects resale value can help an owner-operator or fleet decide whether it makes sense to keep running a truck or sell it while it still has meaningful value.

9 Questions to Ask Before Putting Another 100,000 Miles on Your Semi-Truck

What is the truck worth if I sell it today?
What could it realistically be worth after another 100,000 or 200,000 miles?
What major maintenance or repairs are coming up?
How much have I actually spent on repairs over the last 12 months?
Is downtime becoming more frequent or costing me loads?
Is the truck paid off, or do I still have a significant loan balance?
What would the payment and operating costs look like on its replacement?
Would selling now preserve enough equity to help pay for the next truck?
Am I keeping this truck because the economics still make sense, or simply because it still runs?

Should You Sell a Semi-Truck Before It Reaches 750,000 or 1 Million Miles?

A million-mile semi-truck is not a fantasy. Plenty of well-maintained Class 8 truck or tractors run past a million miles and keep earning. So if the only question were "can this truck keep going," the answer would usually be yes.

But that is not the question that pays your bills. The real question is different: at what point does keeping a high-mileage truck stop making financial sense once you add up repair costs, downtime, reliability, and a resale value that keeps sliding?

That is a business question, not a mechanical one, and the answer is different for every owner.

At Kelly Truck Buyers, we have spent the better part of two decades buying used trucks nationwide, from owner-operators with a single semi to fleets turning over a dozen at a time. We see trucks at every stage of their working lives: fresh trades, tired highway units, wrecks, and everything in between. This article draws on that experience and current industry data to help you think through one decision clearly. Sometimes running a truck as long as it will go is the smartest move. Sometimes selling while it still holds real value is smarter. The goal here is to help you tell the difference.

Can a semi-truck really last a million miles?

Yes, and many do. A well-maintained diesel Class 8 engine commonly runs somewhere between 750,000 and 1.2 million miles before it needs a major overhaul, according to used-truck sellers and diesel parts suppliers who track this closely (Select Trucks, Highway and Heavy Parts).

There is no single magic number, though. Some engines need serious work before 500,000 miles. Others cross a million on original internal parts. The difference comes down to how the truck was run: highway miles at steady RPM are far easier on an engine than stop-and-go regional work, and heavy idling wears an engine in ways the odometer never shows.

So "it still runs" is true for many high-mileage trucks. That is exactly why it is the wrong test. A truck can be mechanically fine and still be a poor financial asset to keep.

What actually starts happening around 500,000 miles

Mileage does not flip a switch. It changes the odds. As a tractor climbs past the half-million mark, several things tend to move in the same unhelpful direction at once.

Repairs get more frequent and more expensive

This is the clearest trend in the data. The American Transportation Research Institute (ATRI), which benchmarks real fleet costs every year, found that industry-average repair and maintenance costs rose 8.6 percent in 2025 to about 21.5 cents per mile, and it flagged aging equipment as a direct cause (ATRI via Heavy Duty Trucking).

Age matters even more than the average suggests. ATRI also found that the smallest carriers, those with fewer than five trucks, had the highest repair and maintenance costs in the truckload sector, partly because they run older equipment. Warranties are a big reason. Powertrain coverage on many trucks runs about five years or 500,000 miles, so a truck crossing that line has usually lost its safety net just as its parts start to wear out.

The first major engine overhaul comes into view

Somewhere in the 500,000 to 1,000,000-mile window, most heavy diesel semis face their first big internal job. The range is wide because duty cycle and maintenance vary so much, but the bill is never small.

An in-frame overhaul, where major wear parts like pistons, liners, rings, and bearings are replaced with the block still in the truck, commonly runs about $15,000 to $25,000 once you add parts, labor, and fluids. A full out-of-frame rebuild, which means pulling the engine and tearing it all the way down, typically runs $25,000 to $40,000 or more (TruckClub, Express Truck Tax).

A rebuild can buy another 500,000 to a million miles of engine life. Whether that is money well spent depends on the rest of the truck, which is the whole point of this article.

Emissions and aftertreatment become a bigger worry

Modern trucks carry a complex emissions system: the diesel particulate filter (DPF), the diesel exhaust fluid (DEF) dosing system, and the selective catalytic reduction (SCR) catalyst. As these age, they fail more often and cost more to fix.

Routine DPF cleaning runs a few hundred dollars, but replacing failed parts adds up fast. A DPF or DOC unit can run $1,500 to $4,000 or more, an SCR catalyst can reach $3,000 to $8,000, and a stacked multi-component emissions failure can top $15,000.

The bigger operational danger is a derate, where the truck cuts its own power over an emissions fault and drops into limp mode, often far from home. That turns a parts problem into a downtime problem, which usually costs more than the part.

Buyers and lenders get more cautious

The used-truck market is not treating all trucks equally right now. In 2026 the strength has been concentrated in late-model, lower-mileage sleepers, while older high-mileage units have not ridden the same wave.

Financing follows the same logic. It is generally harder for the next buyer to get a loan on an older, high-mileage truck, which shrinks your pool of buyers and softens what they can pay. Fewer qualified buyers means a lower number when you sell.

Mechanical life versus economic life

This is the single most useful idea in the whole conversation, so it is worth stating plainly.

A truck's mechanical life is how long it can physically keep running. That can be a million miles or well beyond.
A truck's economic life is how long it keeps making financial sense for your business. That is usually shorter, because rising repairs, growing downtime, and falling resale value eventually tip the math.

The two are not the same, and they do not end at the same time. A neglected truck can outlive its economic life at 450,000 miles. A well-maintained, paid-off truck with a clean history and manageable repair bills can stay economically valuable long after a more cautious owner would have sold. The odometer alone does not tell you which one you have.

The real cost of a repair is not the repair bill

Owner-operators feel this the hardest. When you run one truck, that truck sitting in a shop is your entire income on pause.

A repair almost never costs only what the invoice says. The honest way to add it up looks more like this:

The repair bill itself
Towing or roadside recovery
Lost loads and revenue while the truck sits
Driver pay, lodging, and meals during the delay
Dispatch disruption and possible contract penalties
The real chance of another failure soon after

Industry data backs up how quickly this snowballs. FleetNet America and the American Trucking Associations' Technology and Maintenance Council put the cost of unplanned downtime at roughly $448 to $760 per truck, per day (Millennial's Maintenance summarizing FleetNet and TMC). A single unplanned breakdown, once you fold in towing, repair, driver costs, and lost revenue, commonly runs $3,000 to $9,000, and the truck is typically down about two to two and a half days.

For context, ATRI data put average truckload revenue at about $637 per truck per day in 2024. That is roughly what a single-truck operation gives up for every day it sits, before the repair bill is even paid.

So a $6,000 repair is rarely a $6,000 problem. Add three days off the road, and it can quietly become a $9,000 or $10,000 problem. That number should drive the keep-or-sell decision, not the estimate the shop hands you.

What determines a high-mileage truck's value

Here is the good news for owners of high-mileage trucks: mileage alone does not decide what Kelly or any serious buyer will pay. It is one input among many. Two trucks with 700,000 miles can be worth thousands of dollars apart.

The factors that move the number most:

Maintenance records. Documented, consistent service is often worth more than a lower odometer reading. It is the difference between a known quantity and a gamble.
Engine make and condition, and whether a major overhaul has already been done. A recent, documented rebuild can reset a big part of the value equation.
Engine hours and idle hours. A truck that idled for years carries hidden wear the mileage does not show. Low idle time is a genuine plus.
Transmission condition and how it shifts.
Aftertreatment and emissions history. A clean DPF, DEF, and SCR record removes a major buyer worry.
Tires and brakes, which are immediate, visible costs to the next owner.
Accident and structural history. Frame and collision history matter more than a lot of sellers expect.
Configuration and spec. Sleeper versus day cab, wheelbase, axle setup, and horsepower all affect demand.
Model year and current market demand for that specific truck.
Overall cosmetic and mechanical condition.

Kelly buys across all of these, and we pay particular attention to sleeper tractors. A well-kept sleeper with high mileage, good records, and a sound driveline still has real, saleable value, because there is a steady national market of buyers who want a proven long-haul truck at a used-truck price. High miles do not erase that. Neglect does.

Does it make sense to sell every truck at 750,000 miles?

Some fleets run a fixed replacement policy: instead of squeezing every last mile out of every tractor, they plan from day one to sell at a set number, often somewhere around 700,000 or 750,000 miles. It is a legitimate strategy worth understanding, not a rule everyone should follow.

The case for a set replacement mileage

Selling on a schedule has real advantages:
Predictable capital cycles. You plan and finance replacements instead of reacting to failures.
Avoiding late-life major repairs. You aim to sell before the first big overhaul and the emissions bills that tend to cluster later.
Fewer surprise breakdowns, and more predictable monthly maintenance spend.
More preserved resale value, since you sell while the truck is still in the range buyers and lenders like.
A younger, more reliable fleet, which supports uptime, driver satisfaction, and retention.
Better fuel economy from newer equipment, and often remaining warranty coverage on the trucks you keep.

This is why many fleets trade on the earlier side. ATRI has pegged the industry truck replacement cycle at roughly seven years, and some operations move trucks out far sooner, in the three-to-five-year or 400,000-to-500,000-mile range, specifically to get ahead of the maintenance curve (Fleet Maintenance summarizing ATRI, Engineer Fix).

The case against selling on the odometer alone

Now the other side, because it matters just as much. Replacing a perfectly good, paid-off truck because the odometer hit an arbitrary number can be terrible economics.

A well-maintained 750,000-mile truck you own outright, with a known history and manageable repair costs, may be far more valuable to you than a large monthly payment on a newer one. New Class 8 sleepers run around $170,000 in 2026, up partly due to tariff pressure, and financing that at today's rates is a serious fixed cost. A paid-off truck that needs $8,000 of work a year can still be much cheaper to run than a $2,500 monthly payment.

The right answer is not a number on the dash. It is the math for your specific truck and your specific operation.

A framework for deciding: keep it or sell it

Whether your truck is at 500,000, 650,000, 750,000, or 1,300,000 miles, the same set of honest questions gets you to a clear-eyed decision.

What is the truck worth today? Not what you hope, but what a real buyer would pay this month.
What could it realistically be worth 100,000 or 200,000 miles from now? With depreciation running a bit over one percent a month on Class 8 trucks lately (ACT Research via Trucks, Parts, Service), waiting has a cost.
What major maintenance is coming? An overhaul, aftertreatment work, tires, or a transmission all change the picture.
What have I actually spent on repairs in the last 12 months? Add it up honestly, including downtime.
Is downtime getting more frequent? A rising pattern of breakdowns usually keeps rising.
Is the truck paid off? A paid-off truck earns you more room to keep it.
What would the payment be on its replacement? Compare that real number to your current repair spend.
Would selling now preserve enough equity to help buy the next truck?
Am I keeping this truck because the economics work, or just because it still runs?

That last question is the one most owners skip, and it is often the most important.

Where Kelly Truck Buyers fits

None of this is a push to sell early so we can buy your truck. Sometimes the honest math says keep it, and if you read all of this and decide your 800,000-mile truck is worth holding, that is a good decision.

What Kelly can give you is one hard, useful number in that calculation: what your truck is worth today. We buy nationwide; we consider trucks in nearly any condition, including high-mileage units and trucks needing repairs, and there is no cost or obligation to find out. Knowing that number turns a vague "should I keep it" into a real comparison.

The bottom line

If your truck is closing in on 500,000, 750,000, or even a million miles, you do not necessarily need to sell it. A well-maintained, paid-off truck can keep earning for a long time. But knowing what it is worth right now is what lets you decide whether the next 100,000 miles actually makes financial sense.

If you are weighing that decision, reach out to Kelly Truck Buyers. Tell us honestly what you have, the mileage, the condition, and the repair history, and get an offer. Then decide, with real numbers in front of you, whether keeping the truck or turning its remaining value into your next one is the smarter move for your business.