1. All Cap designs/styles have been "Drop Tested" to meet DOT qualifications for HWY Transportation Fuel Tank safety. FMCSA-39367

2. Always measure the inside diameter (ID) of Fuel Cap for a more positive Identification if there is any question as to which Cap to use.

3. Should the Cap not be available - measure the outside diameter (OD) of the Fill Tank Neck to determine inside Diameter (ID) of Cap.

4. Always make sure and if the Tank is either Vented or non-Vented in order to spec correct Vented or Non-Vented Cap.

(note: a Vented Cap is made to work with a non-Vented Tank; it is also safe to use on a Diesel Fuel Tank that is already Vented) a non-Vented Tank Must have a Vented Cap to operate properly.

5. The inside diameter (ID) of Caps used with Low-Sulfur labeled Diesel Fuel Tanks are smaller and have different treads than Caps used with Diesel Fuel Tanks that have no Low Sulfur Label.

6. All Caps are Threaded Female style. (except the Peterbilt Lever Style and Freightliner Cam-Cap Style)
Some Older Fuel Tank fill necks (pre 2000) may have a different size and thread than current Tanks.

7. Though Steel Tanks are not as common in the HD Truck Industry as Aluminum, it is recommended to clarify whether the tank is Aluminum or Steel.

8. NPSM Threaded Caps will not fit NPSL or NPT Fill Neck Threads. However, NPSL will fit NPSM threaded Fill Necks.

Terminology Definitions

SCH Schedule

NPSM National Pipe Straight Medium

NPSH National Pipe Straight Hose

NPSL National Pipe Straight Loose

UNNS United National Non-Standard

UN United National

Triple Lead Three Starts – Threads

NS Non-Standard

Bail End of chain connection

Full Function Thermal – Pressure – Vented

Thermal Relief Over Temp Safety Feature

Pressure Relief Over Pressure Safety Feature