Glossary
Dead Mileage
Direct Answer / TL;DR
What is Dead Mileage?
Miles driven that don't contribute to a productive purpose — such as driving to a petrol station that's out of your way. Dead mileage burns fuel and costs money without advancing your journey.
Why does it matter for UK drivers?
Dead mileage is a concept borrowed from logistics and fleet management, where it refers to distance driven without a paying load (empty returns, positioning journeys). For individual drivers, dead mileage is any distance covered that isn't part of your actual intended journey.
A detour to a cheaper petrol station creates dead mileage equal to the round-trip distance to the station (assuming it's not on your route). This dead mileage has two costs: the direct fuel cost (which WorthThePump calculates), and the indirect time cost (which varies by driver and isn't modelled).
For commercial operators, dead mileage is a key KPI. A courier company tracks 'productive miles per gallon' — factoring in all the positioning and empty return miles. A vehicle averaging 30 MPG on loaded journeys but 25% of its mileage is dead returns effectively costs more per productive mile than the MPG figure suggests.
For personal drivers, the practical implication is to factor in whether the cheap petrol station will be on your route at some point naturally. Passing a Tesco Extra on your commute home twice a week eliminates the dead mileage entirely — the detour cost is zero. In this case, the net saving equals the gross saving.
The WorthThePump calculation assumes the station is a pure detour from your current position. If the station is on your planned route, your actual net saving is higher than calculated (the dead mileage cost is zero). Conversely, if you'd need to backtrack significantly, the actual cost could be higher than the straight-line Haversine estimate.
Related terms
Further reading
Now you know what Dead Mileage means —
find out if your nearest cheap station is actually worth the trip.