💰 How Fuel Cost Is Calculated

AutoDrive estimates the fuel cost of every drive on the server. The formula depends on whether your vehicle runs on gas or electricity:

Gas / diesel: (Drive Distance ÷ Avg MPG) × Retail Price per Gallon
Electric: (Drive Distance ÷ mi/kWh) × Price per kWh

Avg MPG is the average of your vehicle's City and Highway MPG, set during VIN decoding or entered manually on the vehicle profile. If both are missing, AutoDrive falls back to 25 MPG (close to the current US fleet average). EVs use a 3.5 mi/kWh efficiency baseline.

Price per gallon is resolved in this order — first match wins, and the drive details screen shows you which one was used:

• Your last fill-up for this vehicle — the price you paid the most recent time you logged fuel for the specific vehicle the drive is on. Beats every other source for accuracy.
• Your group's recent average — mean price per gallon across the last 60 days of fuel logs in your active account group. Useful when this vehicle is new but other vehicles in the household are tracked.
• US Energy Information Administration (EIA) — official weekly retail prices, scoped to the regional PADD (East Coast, Midwest, Gulf Coast, Rocky Mountain, or West Coast) when the drive has start coordinates, otherwise the US national series. EIA updates every Monday.
• National average fallback — only used if EIA is unreachable, so cost estimates never silently return $0.

Your vehicle's fuel type (regular, mid-grade, premium, or diesel) drives which EIA series is queried, so a diesel truck and a premium-only sports car each get the correct pump price.

Electric vehicles are detected automatically (your vehicle's type is marked as EV). The cost is calculated from your last 90 days of charging logs — total cost ÷ total kWh gives your real $/kWh, which is then multiplied by the drive's estimated kWh use. If you have no charging history yet, AutoDrive falls back to a US residential average of $0.16/kWh.

The estimate fills in automatically whenever a drive is saved without a manual cost, even when start coordinates are missing — AutoDrive will use your fuel/charging history or the EIA national series instead of skipping the estimate. If you enter a cost yourself, your value is always kept.

This is still an approximation. Real fuel consumption varies based on driving style, traffic, terrain, and vehicle condition; EIA prices are regional averages that can be a few cents off the pump near you. For the most accurate cost history, log your fill-ups and charges — once you have a few logged, AutoDrive will prefer your real pricing over any regional average.