Best DEF Tank Cap Reviews


It is easy for consumers to overlook critical elements that can cause big headaches, such as storage units made from the wrong material or def pumps with incorrect seals. A DEF cap is the final essential part of the chain.

Do not make the tempting mistake of believing that all fuel caps are identical. Each stage of the supply chain echoes the same information. DEF cannot be altered. It is essential to choose the best DEF tank caps.

What is a Diesel Exhaust Fluid Cap (DELF)?


The DEF cap is a simple way for a driver to fill up an engine with diesel exhaust liquid and seal it.

A DEF cap is necessary to keep DEF in the tank for obvious reasons. It is the fundamental responsibility to keep debris out. These small details are essential, and skilled operators will keep several DEF caps in their arsenal.

Damage to an engine can result from debris entering the SCR.

What does a DEF Tank Cap do?

Cracked or loosely fitting DEF caps can allow fluid to leak into the filler. DEF is corrosive for various metals; you must not pool near fuel openings. There is a possibility of contamination in the fuel system and a small DEF can damage a diesel engine in fuel.

The SCR relies on steady, consistent DEF flow into the structure. The stream will be affected if there is no substantial backpressure. It would help to tighten the DEF cap to maintain the correct pressure.

Poorly fitting storage and transfer connections can cause significant problems for DEF. Diesel exhaust fluid is mainly deionized water. Water evaporates. The SCR relies on a particular mix of 32.5% Urea and 67.5% Water. This combination could cause severe damage to the entire system.

Both the EPA and the API have protocols to handle DEF at each stage of the supply chain. It is essential to choose a suitable material for a DEF cap.

When shopping for this tiny but essential part, consider the following guidelines. These caps are only for diesel exhaust fluid.

  • Stant 105525 Diesel Exhaust Fluid Cap by Stant

Stant was founded in 1898 and is a global company that specializes in OEM and consumer automotive products. The company provides a complete line of fuel caps. The 10525 is non-corrosive and has a standard (40mm) opening.

The 10525 is compatible with all class 6-8 trucks, Reefers included. The cap is marked as a DEF cap in bright blue, matching the diesel fuel cap and contrasting the color for heavy-duty commercial use.


A quality company that offers a long-lasting product with a warranty

Keys color-coded to match DEF cap


  • Freight Defense 100302 – Locking DEF Cap by Freight Defense

VSI, Freight Defense’s parent company, has manufactured commercial diesel engine parts for over 50 years. The company sells via Amazon and other retail avenues. The 100302 is a typical commercial-grade DEF cap designed for Freightliner/Peterbilt/Kenworth and Western Star.

The 100302 has a corrosion-resistant coating on each piece. This DEF cap was designed for Ford F250-750.


A dedicated heavy-duty truck company can perform commercial construction

For DEF. You might consider purchasing the fuel cap.


Retail consumers find it too expensive.

  • Ronin Factory Combo Package for Cummins Diesels By Ronin Factory

Ronin Factory is exclusive and sells auto parts through Amazon. The company produces a host of products for Amazon. It is a brilliant idea to buy both the fuel cap and the DEF cap simultaneously. The combination of colors determines whether Diesel or DEF. These caps can be used as a factory replacement on 2013+ Dodge trucks.


A manufacturer that specializes in heavy-duty construction

Both caps are marked for Diesel or DEF.


Before you buy, confirm the fit.

What can you Look for in a DEF Tank Cap?

You don’t need to spend a lot of time choosing the suitable DEF storage container and pumps. Then, you can buy a cheap DEF cap. Caps for DEF must be able to withstand extreme temperatures and humidity. DEF caps should be non-corrosive, above all else.

You can find Blue DEF caps on DEF tanks because the neck is often placed on the same side of the fuel. It is easier to contaminate the DEF tanks so close to fuel. DEF tank openings can be smaller than diesel.

Check that the DEF cap is sealed correctly. Before filling, it is a good idea to clean around any openings. DEF tanks offer no filtration like diesel fuel tanks. One-tenth of one teaspoon of DEF can contaminate 5 000 gallons of diesel fuel.

The Key Takeaways

When purchasing equipment, be aware of the DEF properties. Consider evaporation in hot and humid areas. Cool areas can be dangerous because water expands when frozen. OEM resources are available from every automotive, industrial, and off-road manufacturer, and this brand offers a long-lasting partnership.

The best DEF tank caps should not touch any metal other than stainless. It would be best if you dared not forget about contamination.

DEF tanks can be contaminated by small amounts of fuel, oil, and other fluids. Over the next few decades, industry standards ( ISO22241-3 ) will be more stringent at every supply chain.



Please enter your comment!
Please enter your name here