Diesel vs Gas: The 2025 Fleet Cost Trap

Why sticking with diesel specs might be the most expensive decision your fleet is making right now.

Author

Leyhan Hansen
July 14, 2025

A public works department in the Northeast had always gone diesel.

Every new Class 5 or 6 truck? Diesel. No questions asked.

But in 2025, that decision backfired—hard. Fuel prices spiked. DEF became a logistics mess. And they started losing trucks for days at a time waiting on emission repairs.

After 7 breakdowns and $23,400 in unplanned maintenance, they had to ask: Is diesel still worth it?

Diesel vs Gas: The 2025 Fleet Cost Trap

Real Fleet Cost Breakdown (Gas vs Diesel)

Category

Diesel

Gas

Upfront Cost

+$7,500

—

Annual Maintenance

$2,000+

~$1,200

DEF System Repairs

$800 avg

N/A

Fuel Cost (2025 Avg)

$4.25/gal

$3.60/gal

Downtime Loss

4 days/year x $500

1.5 days/year x $500

Resale Value (8 yrs)

+$3,500

Base

🔍 Tip: Search “diesel prices near me” to check your local spread.

Bottom line? You’re not just paying more upfront. You’re stacking risk into every daily operation.

DEF Isn’t Just Annoying—It’s Expensive

The keyword “DEF locator” gets searched over 27,000 times per month.

Why? Because even drivers know DEF refills are a pain. DEF system failures have become one of the most common downtime causes in Class 3–6 trucks.

Popular related searches:

  • def location near me

  • def locator app

  • def of location

Try it yourself → Yara DEF Locator App

⚠️ A $2 DEF sensor can shut down a $90,000 truck.

Diesel Power vs ROI: What Fleets Forget

Metric

Diesel

Gas

Horsepower

330 HP

385 HP

Torque

750 lb-ft

430 lb-ft

Best Use Case

Heavy tow / PTO

Mixed duty

⚠️ If your average route is 30 miles and your payload isn’t maxed? Gas is more than enough.

When Diesel Actually Makes Sense

Not all diesel specs are bad. These are the only times it may be justified:

Off-Road Fire Trucks

Diesel is safer to store and refill on wildland scenes or when refueling is remote.

High Mileage Fleets

If your fleet logs 20,000+ miles per year, diesel might pay back its upfront cost.

Continuous High Idle + PTO

Certain hydraulic setups require diesel—but check if gas + add-on idle system can handle it.

Diesel vs Gas Upfit Comparison Chart (Download)

Want to see exactly where diesel or gas makes sense?

Download our free Upfit Setup Comparison for:

  • Class 3–6 truck examples

  • Hooklift, dump, service, landscaper, and more

  • Idle hours, torque needs, and fuel ROI side-by-side

Diesel vs Gas Upfit Comparison Chart.pdf57.78 KB • PDF File

Fleet Manager’s Final Spec Checklist

Before you spec your next fleet order, ask yourself:

  • Are we really using the diesel torque?

  • Can our mechanics handle modern diesel repairs?

  • How many idle hours do we log per week?

  • Will we keep this truck past 125K miles?

  • What’s the cost of 3 days of downtime?

If the math doesn’t work? Diesel doesn’t either.

Wrap-Up: Spec Smarter. Save Bigger

⚠️ Don’t let outdated diesel specs cost your fleet another $50K this year.

🧠 Join 100+ Founding Members of The Upfit Insider and get:

  • Full-spec teardown PDFs

  • Behind-the-scenes videos

  • Real-world strategies from the field

🎯 Know a fleet still defaulting to diesel?
Forward this to them.
Let’s stop spec’ing trucks like it’s 2005.

—
Leyhan
Founder, The Upfit Insider

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