Red diesel, commonly called off road diesel, is dyed fuel formulated for agricultural, construction, and other non-highway equipment with reduced tax rates. Using it in a truck violates regulations in most regions because trucks must operate on on-road taxable diesel. The red dye makes illegal use easy to detect during roadside checks or audits. Although the engine may run on it, risks include substantial fines, potential emission system damage, and legal penalties. Proper on-road diesel ensures compliance and reliable performance.