can you mix def fluid brands

When it comes to maintaining your diesel engine, DEF fluid, also known as Diesel Exhaust Fluid, plays a crucial role. But what happens when you run out of a certain brand of DEF fluid and need to use a different one? Can you mix DEF fluid brands? Let’s find out.

Understanding DEF Fluid

In order to understand whether you can mix DEF fluid brands, it’s important to first understand what DEF fluid is. Diesel Exhaust Fluid is a non-hazardous solution made up of 67.5% demineralized water and 32.5% high-purity urea. It is injected into the exhaust stream of diesel engines to reduce harmful emissions.

Compatibility of DEF Fluid Brands

The compatibility of DEF fluid brands depends on various factors, such as the quality of the fluid and its certification. The American Petroleum Institute (API) has established certified standards for DEF fluid, known as the API certification. When purchasing DEF fluid, it’s essential to look for the API certification label, which ensures the fluid meets the required quality standards.

In general, it is safe to mix DEF fluid brands as long as they are all API certified and meet the required quality standards. The composition of DEF fluid is standardized, so mixing different brands should not cause any chemical reactions or compatibility issues.

Benefits and Risks of Mixing DEF Fluid Brands

Mixing DEF fluid brands can offer several benefits, such as:

  • Availability: Sometimes a particular brand of DEF fluid may not be readily available. In such cases, mixing brands can help in ensuring a continuous supply of DEF fluid.
  • Cost-Effectiveness: Mixing brands may be a more cost-effective solution, especially if one brand is available at a lower price compared to others.

However, there are also some risks involved in mixing DEF fluid brands:

  • Quality Assurance: It is crucial to make sure all the DEF fluid brands being mixed are API certified to ensure the required quality standards are met.
  • Warranty Consideration: Some engine manufacturers recommend using a specific brand of DEF fluid to maintain warranty coverage. Mixing different brands may void the warranty, so it’s essential to check the manufacturer’s guidelines.

Storage and Handling Considerations

When storing or handling DEF fluid, it’s important to follow some guidelines to maintain its quality:

  1. Store DEF fluid in a cool and dry place, away from direct sunlight.
  2. Avoid contamination by using dedicated equipment and avoiding contact with dirt, dust, and water.
  3. Use DEF fluid within its shelf life as indicated on the packaging.

By following these storage and handling considerations, you can ensure the DEF fluid maintains its effectiveness regardless of the brand being used.


In conclusion, it is generally safe to mix DEF fluid brands as long as they are all API certified and meet the required quality standards. However, it’s essential to consider the potential risks, such as warranty implications, and ensure proper storage and handling to maintain the effectiveness of the fluid. When in doubt, it’s always advisable to consult the manufacturer’s guidelines or seek professional advice.