Emulsifier vs. Demulsifier: How Should Diesel Additives Handle Water?

Water in diesel fuel is a serious concern. It can contribute to corrosion, filter plugging, microbial growth, injector problems, and fuel system wear.

What Is an Emulsifier?

An emulsifier helps disperse water into the fuel so it remains suspended. Some products use this approach, but it can carry water farther through the fuel system.

What Is a Demulsifier?

A demulsifier helps water separate from the fuel so the fuel/water separator can do its job. This approach is commonly preferred by many diesel engine and fuel system manufacturers.

Opti-Lube’s Approach

Opti-Lube diesel fuel additives are designed to support water separation. The goal is to help water drop out of suspension so it can be removed by the vehicle or equipment’s water separator rather than carried through the fuel system.

Best Practice

Keep tanks as clean and dry as possible, drain water separators as needed, and use a fuel additive that supports the way your fuel system is designed to handle water.

Need help choosing? Start with Opti-Lube diesel fuel additives or review our FAQ for dosing, storage, and compatibility questions.

Fungicides and Biocides in Diesel Fuel

Microbial growth in diesel fuel is often called diesel bug. It is commonly described as algae, but the problem usually involves bacteria, fungi, or other microbes that grow where water and fuel meet.

Why Water Matters

Microbes need water to grow. If a tank has water at the bottom, the fuel/water interface can become a place for microbial growth. This can lead to slime, sediment, plugged filters, corrosion, and fuel quality problems.

What a Biocide Does

A diesel biocide is designed to kill microbial contamination. It can be useful when contamination is present, but it is not a substitute for good tank maintenance. Dead microbes and debris may still need to be filtered or removed.

Prevention

• Keep fuel tanks clean and dry.
• Drain water when needed.
• Use proper filtration.
• Inspect stored fuel regularly.
• Use stabilizer and treatment products appropriate for the storage situation.

Need help choosing? Start with Opti-Lube diesel fuel additives or review our FAQ for dosing, storage, and compatibility questions.