Compare gas and diesel truck costs from purchase through resale using your prices, fuel economy, driving miles, and annual upkeep estimates.
Calculation details
Table of contents
How to use our Diesel vs Gas Truck Lifetime Cost Calculator
- Enter the same planned ownership period in Years you will keep the trucks and realistic Miles driven per year for both trucks.
- Copy comparable purchase quotes into each out-the-door price field, then estimate each truck's value at the planned sale date.
- Enter MPG and local pump prices for the expected mix of normal driving and towing. Open Advanced options to include maintenance, repairs, DEF, and other diesel-only costs.
- Click Calculate. A positive Lifetime cost difference means diesel costs less over your planned ownership period; a negative value means gas costs less.
- Sanity-check the result by confirming that the diesel payback occurs before your planned sale and that both trucks use MPG and fuel prices for the same type of driving.
Definitions
Out-the-door price: The purchase amount including the parts of the deal you choose to count, such as taxes, title, dealer fees, and installed options.
Resale value: The estimated sale or trade-in amount received when you stop owning the truck.
MPG: Miles per gallon, or how far a truck travels on one gallon of fuel. Higher MPG uses fewer gallons for the same distance. [1]
DEF: Diesel exhaust fluid, a consumable used by many modern diesel emissions systems.
Diesel purchase premium: Diesel truck out-the-door price minus gas truck out-the-door price.
Cost per mile: Estimated lifetime cost divided by total miles driven during ownership.
Common mistakes and quick fixes
Mistake: Entering MSRP instead of the Gas truck out-the-door price or Diesel truck out-the-door price.
Fix: Use comparable quotes that include the same taxes, fees, and installed options.
Mistake: Using highway MPG for one truck and towing MPG for the other in Gas truck fuel economy and Diesel truck fuel economy.
Fix: Enter a real-world average for the same expected driving and towing mix.
Mistake: Treating Regular gas price and On-highway diesel price as the same price.
Fix: Enter the separate local $/gal prices from a pump sign, receipt, or fleet statement.
Mistake: Leaving an unrealistic Gas truck expected resale value or Diesel truck expected resale value in place.
Fix: Use trade offers or comparable listings for the expected age and total mileage at sale.
Mistake: Counting DEF inside Diesel maintenance and repairs and again in DEF and other diesel-only costs.
Fix: Put each recurring cost in only one field to avoid double counting.
Mistake: Reading a negative Years before or after planned sale as a diesel win.
Fix: A negative value means the purchase premium is expected to pay back after you plan to sell.
Limitations & Key Assumptions / Boundary Conditions
- The estimate includes purchase price, resale value, fuel, and the annual allowances entered for maintenance, repairs, DEF, and other diesel-only costs.
- It excludes financing, insurance, registration, downtime, towing equipment, taxes not included in the out-the-door quote, and costs not entered in the annual allowances.
- Both trucks are assumed to travel the same annual miles and be sold after the same number of years.
- Fuel prices, MPG, repair costs, and resale values can change. Replace example values with local prices, observed MPG, service records, and current trade or resale estimates.
- Payback compares the diesel truck's higher purchase price with annual operating savings only. It excludes resale value because resale money is received when the truck is sold.
- A result after the planned sale means the diesel purchase premium is not recovered during the ownership period, even if diesel has a lower lifetime cost after resale is included.
Methodology
Lifetime cost calculation
The calculator uses the same ownership years and annual miles for both trucks. It converts miles and MPG into annual gallons, then adds fuel and entered annual costs to the purchase price minus expected resale value.
total ownership miles = miles driven per year * years you will keep the trucks
annual fuel cost = miles driven per year / fuel economy in MPG * fuel price per gallon
gas lifetime cost = gas out-the-door price - gas expected resale value + gas annual operating cost * ownership years
diesel lifetime cost = diesel out-the-door price - diesel expected resale value + diesel annual operating cost * ownership years
lifetime cost saved with diesel = gas lifetime cost - diesel lifetime cost
Payback and signed results
Annual operating cost includes fuel plus the entered annual allowances. For diesel, the allowance can include maintenance, repairs, DEF, and other diesel-only costs. A positive lifetime-cost savings value means diesel costs less; a negative value means gas costs less.
annual operating cost saved with diesel = gas annual operating cost - diesel annual operating cost
diesel purchase premium = diesel out-the-door price - gas out-the-door price
diesel payback years = diesel purchase premium / annual operating cost saved with diesel
Payback is shown only when diesel has both a higher purchase price and positive annual operating savings. Otherwise, payback is N/A. The timing margin is planned ownership years minus payback years, so a negative margin means payback happens after the planned sale.
Worked mini-example
For 12,000 miles per year, 15 MPG gas at $3.50 per gallon costs $2,800 per year for fuel. At 22 MPG, diesel at $4.00 per gallon costs about $2,181.82 per year for fuel. With $1,500 gas maintenance, $1,400 diesel maintenance, and $200 diesel-only costs, diesel saves about $518.18 per year in operating cost. A diesel purchase premium of $8,000 would therefore take about 15.44 years to pay back.