NOTE: These caps DO NOT fit pick-up trucks or smaller duty vehicles.

These are ONLY for heavy-duty sized semi-trucks.

40mm DEF Cap Diesel exhaust fluid (DEF) has become an essential part of a truck’s fuel system, as it aids in the selective catalytic reduction that improves the efficiency of fuel burn. The systems, while relatively new, have become a hallmark due to federal regulations.

That said, DEF has added another aspect of maintenance for trucks, as it’s expendable and leaves the system open for additional issues. Those issues can at least partly spawn due to poor protection of the intake area, which you can secure by using a 40mm DEF cap such as this.

This DEF cap is corrosion-proof and weather-resistant, and it includes a tether to keep it near the area without having to worry about losing it. This cap helps to prevent spills, overflows, and leaks, as the DEF cap fits most Class 6 and 8 trucks, with the exception of Volvo and Mack.

Its distinctive blue color will allow for quick identification and appropriate maintenance. Contact us today to ask any questions you might have about our 40mm DEF caps.