How to Create Hanging Car Diffusers Using The MWFC Reed Diffuser Base

Before choosing a fragrance, always check its IFRA documentation to confirm the maximum allowed usage rate for Category 10A.

Our recommended starting formula is:

4 parts Reed Diffuser Base : 1 part Fragrance Oil = 20% fragrance load

Important things to keep in mind:

• Not every fragrance is approved at 20%- you can find all MWFC compatible fragrance oils here!
• Your total fragrance load must stay within IFRA guidelines
• Higher fragrance loads may impact performance or cause oversaturation

Vehicles are small, enclosed spaces, so proper formulation and testing are especially important.

Staying compliant protects both your customers and your business.

Before mixing anything:

• Decide your diffuser size (For this demonstration, we’re making 10 (10mL) diffusers.)
• Confirm the IFRA usage rate for your chosen fragrance
• Calculate your base-to-fragrance ratios

You can use this calculator to do the math for you: 👉 MWFC Fragrance Oil Calculator 

This step helps avoid extra work and keeps your testing process clean.

*Note: Because the car diffuser bottles are so small, I recommend making these in a bulk batch and then pouring into the containers once mixed! That is the process we are going to follow and for this example we are going to make 10 (10ml) hanging car diffusers with one scent. 

Step 1:

Weigh 64 g of reed diffuser base into a clean container. 

Step 2:

Add 16 g of fragrance oil.

This creates the recommended 4:1 ratio, which equals a 20% fragrance load.

Step 3:

Mix for 30 - 45 seconds, until the mixture is fully blended with no separation.

Step 4:

Carefully pour the mixture into your hanging car diffuser bottles using a pipette or small funnel to avoid spills.

Secure the stopper and cap tightly.

Step 5:

Allow the diffuser to cure for 24 - 48 hours before evaluating performance.

Step 6:

To test, remove the lid and stopper from the diffuser. Twist the wooden lid back on, then tilt the car diffuser until the top of the wooden lid is fully saturated. Secure the stopper once again to avoid possible spillage, then twist the lid back on.

When fragrance is no longer coming from the diffuser, repeat this process.

Step 7:

Before selling, it is very important to test your car diffusers due to heat fluctuations in cars and airflow changes while driving.

Here is how to properly ensure your diffuser is ready to hit the shelves:

• Test in multiple temperature conditions
• Monitor for leakage
• Ensure the cap and plug seal properly
• Confirm fragrance strength is appropriate (not overpowering)

Testing protects your customers and your brand reputation.

Car diffusers are trending right now, and they appeal to a wide range of customers- and best of all? They aren't complicated.

By following this simple step-by-step guide, following IFRA guidelines, and proper testing, car diffusers can become an easy product addition that customers always reach for.

Take the time to test each fragrance, note your results, and refine your process as needed.

More helpful resources: 

• How To Make Home Reed Diffusers 
• Reed Diffuser FAQs + Troubleshooting (COMING SOON)
• Fragrance Oils over 20% in IFRA Category 10A (often works well for Reed Diffusers)
• General Fragrance Oil Calculator