 You may not know this, but you are breaking the law. The small savings you see at the pump could end up costing you up to $5,000 in fines. Dyed diesel fuel is not taxed and is intended for off-road use only. Please, do the right thing. Don't use dyed fuel on Montana's roads. To report violators, you can call 1-888-FUELLAW. Thanks for your help. This message brought to you by the Montana Department of Transportation.