Diesel vs Gas Cost Comparison
Compare annual fuel costs between diesel and gasoline trucks based on price, MPG, and mileage.
Results
Visualization
How It Works
Diesel engines provide significantly better torque and fuel efficiency than gasoline engines, which is why they dominate heavy-duty trucking. However, diesel fuel usually costs more per gallon than gasoline. The total cost comparison depends on the price spread between fuels, the MPG difference, and total annual mileage. For high-mileage applications, diesel almost always wins on total cost.
The Formula
Variables
- Diesel Price — Current diesel fuel price per gallon
- Gas Price — Current gasoline price per gallon
- Diesel MPG — Fuel efficiency of the diesel vehicle
- Gas MPG — Fuel efficiency of the gasoline vehicle
- Annual Miles — Total miles driven per year
Worked Example
At 120,000 annual miles: A diesel truck at 6.5 MPG and $4.10/gallon uses 18,462 gallons costing $75,692. A gas truck at 8.0 MPG and $3.50/gallon uses 15,000 gallons costing $52,500. In this case, gas is $23,192 cheaper annually. However, diesel engines last 2-3x longer, which can offset the fuel cost difference over the life of the truck.
Practical Tips
- Consider total cost of ownership, not just fuel — diesel engines typically last 750,000-1,000,000 miles vs 200,000-300,000 for gas.
- Diesel engines produce more torque at lower RPMs, making them more efficient for heavy hauling and mountain terrain.
- Gas trucks may have lower maintenance costs (no DEF, simpler emissions systems) that offset some fuel cost differences.
- For medium-duty trucks (Class 3-6), the diesel vs gas decision is closer — run the numbers for your specific use case.
- Factor in resale value — diesel trucks typically retain higher resale value in the commercial truck market.
Frequently Asked Questions
Why is diesel more expensive than gasoline?
Diesel costs more due to higher federal and state taxes, increased demand from commercial trucking and heating oil markets, and stricter refining requirements for ultra-low sulfur diesel (ULSD). The price premium is typically $0.30-$0.80 per gallon.
Is diesel better than gas for trucking?
For heavy-duty (Class 7-8) trucking, diesel is universally preferred due to superior torque, engine longevity, and fuel efficiency under heavy loads. For medium-duty and light commercial vehicles, gasoline is increasingly competitive.
How much longer do diesel engines last?
Diesel engines in commercial trucks typically last 750,000 to over 1,000,000 miles with proper maintenance. Comparable gasoline engines usually need major overhaul or replacement at 200,000-300,000 miles.
Does DEF add to diesel operating costs?
Yes, Diesel Exhaust Fluid (DEF) adds about $0.01-$0.02 per mile in operating cost. A truck uses approximately 2-3% as much DEF as diesel fuel. At $3-4 per gallon for DEF, this is a minor but real added cost.
Are electric trucks cheaper to operate than diesel?
Electric trucks have significantly lower fuel (electricity) costs — roughly $0.15-$0.25 per mile vs $0.55-$0.70 for diesel. However, their much higher purchase price, limited range, and charging infrastructure challenges currently limit adoption to specific short-haul routes.