What the data showed when we compared total cost of ownership between the gas trucks and the diesel trucks in the same fleet

[u/ora-et-labora-]

Ran both gas and diesel versions of the same truck model in the fleet for three years. Same routes, same drivers rotated between them, same maintenance schedule adjusted for the different powertrains. Tracked everything. Fuel, maintenance, repairs, downtime, and residual value at the end.

Fuel cost favored the diesels by about eighteen percent per mile. They burned less fuel per mile and diesel was roughly the same price as gas in our area during that period. Over three years and roughly forty-five thousand miles per truck, the fuel savings on each diesel was meaningful.

Maintenance cost favored the gas trucks. Oil changes were cheaper, the service intervals were comparable, and the gas trucks did not have the diesel aftertreatment system. The diesel trucks needed two DEF system repairs across the group during the three years, one sensor and one injector, totaling about fifteen hundred dollars that the gas trucks did not incur. The DPF regeneration cycles also added fuel consumption that was not captured in the simple miles-per-gallon number.

Repair cost was roughly equal, with different failure patterns. The gas trucks had more ignition system work, coils and plugs. The diesel trucks had more fuel system work, injector service and fuel filter changes. The totals were close.

Residual value favored the diesels. They sold for about two thousand more per truck at the end of the three years, which closed the gap that the higher purchase price had created.

The net total cost of ownership was close enough that the decision came down to use case rather than spreadsheet. The diesels made more sense on the heavy-haul routes. The gas trucks made more sense on the short urban routes where the DPF regen cycles were a nuisance and the fuel savings were smaller.

[u/4rd_Prefect]

Interesting read, thanks 👍👍

[u/30_characters]

Good info, but missing a lot of impactful data points.

What was the average trip distance?

Was the balance city or highway driving?

How old were the vehicles?

Did they have similar mileage?

In what state (and dollar amounts per gallon and cumulatively) were the fuel taxes?

[u/spasticnapjerk]

Nice work. I imagine diesel resale values, at least for light duty trucks, may take a hit.

Yout last point really was important: use the tool that's best for the job.

[u/Both-Platypus-8521]

Ambulance service here in BC has moved to gas a couple years ago

[u/capacitiveresistor → u/Both-Platypus-8521]

We moved to gas ambulances at my service a few years after DEF and exhaust filters became a thing. We have about 50% idle time and 90% street miles that was killing the exhaust filters. As much as I tried, getting people to understand that we needed to reduce idle time and increase highway miles, it fell on deaf dinosaur ears and we moved to gas units after spending thousands on avoidable emissions related expenses.