Off-road diesel vs on-highway diesel: why the price is different

Off-road (dyed) diesel is cheaper than pump diesel because it is sold without the road taxes: the federal excise tax on highway diesel, and in many cases state fuel taxes, do not apply to fuel used off the public roads, in equipment like mining trucks, gensets, locomotives, and construction machines. The red dye exists to mark untaxed fuel; using it on-road is illegal. The fuel itself is the same No. 2 diesel.

What makes up your delivered price

Start from the regional retail or rack price, remove the taxes that do not apply to your use, add delivery. Federal excise on highway diesel is 24.4 cents per gallon (as of this writing; verify current rates), and state treatment varies widely, which is why two sites in different states can pay meaningfully different net prices for identical fuel. This is the same netting arithmetic the EBM™ platform runs weekly from EIA regional data to price identified fuel for off-road fleets, and it is why our calculator prefills different defaults for on-highway and off-road engine classes.

The number that matters more than the discount

The tax exemption is real money, but it applies to every gallon including the wasted ones. An engine burning above its certified combustion target wastes dyed gallons exactly as fast as taxed ones. The cheapest gallon is still the one you do not burn.