When a thermoplastic elastomer (TPE) part fails an automotive “fogging” requirement, it can turn into a customer complaint fast. This case study shows how this process oil supplier helped one TPE producer move from “over the limit” to a safer, automotive-ready outcome. Questions? Contact us.
Fogging problems don’t always announce themselves on the production floor. Your TPE can run smoothly and still miss your customer’s interior spec later, when heat-driven volatility and appearance expectations get tested.
In this latest case study in our “processing problems” series, we share a real-world example (with details generalized) that shows:
- What the customer noticed
- What we reviewed
- What changed
- The results
Suzanne Kingsbury, Director of Quality
The Problem: Fogging Higher Than an Automotive Interior Requirement
Our customer produces a TPE material used in automotive interior components. In routine testing, they measured fogging higher than the interior requirements set by a major automotive producer (original equipment manufacturer, or OEM).
This mattered because fogging is not just a “lab number.” In the vehicle, it’s the film that can collect on the inside of the windshield (and other glass) and create a hazy layer that can obstruct visibility.
The customer’s goal was simple: meet fogging requirements without creating new processing or performance problems.
A Common Root Cause: Volatility and Outgassing from Interior Polymers
Before we jump into the solution, it helps to define what fogging tests are really measuring.
Many automotive interior parts are polymer-based (plastics, elastomers, foams, coated fabrics). Under heat, volatile and semi-volatile compounds can migrate out of the material. Those compounds can then condense on cooler surfaces (like glass), leaving behind a visible film.
In many TPE systems, one place to quickly check is the oil used for processing and soft-touch performance. If that oil does not have controlled volatility, it can contribute to higher fogging results.
What This Process Oil Supplier Looked at First
Rather than guessing, we reviewed the formulation variables that most commonly drive fogging failures in TPE:
Start by checking the basics across recent production.
- Did the specialty oil source or grade change?
- Was there a change in polymer grade?
- Did the additive package or treat rate change?
- Were there process temperature changes (or longer residence time)?
- Did storage conditions shift for pellets, parts, or packaged goods?
Then we narrowed in on a practical principle for fogging control: lower volatility extender oil usually helps.
The Solution: Chevron ParaLux 6001 for Lower Volatility and Automotive Readiness
We recommended Chevron ParaLux 6001, a specialty oil grade used in automotive interior applications where fogging needs to be minimized.
Why this direction helped:
- Higher flash point supports lower volatility under heat (a key driver in fogging performance).
- Higher molecular weight generally means less tendency to “boil off” or migrate compared to lighter options.
- Automotive approvals make it a safer bet when you need to meet stringent interior requirements.
In plain terms: we aimed to minimize the amount of “evaporable” material that could leave the TPE and show up on the windshield in fogging tests.
Validation: Sample, Test, Then Standardize
As always, the customer tested samples in their own formulation and processing conditions. After confirming the performance direction on fogging, they moved forward with ParaLux 6001 for ongoing production.
That in-house validation matters because fogging results can be influenced by multiple variables. The best outcome comes from testing the full system (polymer + specialty oil + additives + process conditions), not relying on one data point in isolation.
A Practical Checklist for Process Oil Supplier Conversations About Fogging
If you’re troubleshooting a fogging failure (or trying to prevent one), here’s a simple way to pressure-test the likely causes.
Start with a quick review of potential changes and conditions.
- Raw material changes (especially the specialty oil, polymer, and additives)
- Processing temperatures and residence time
- Storage time/temperature for pellets, molded parts, and packaged goods
- Any shift in the customer’s test method or limit
Then compare candidate specialty oils with fogging performance in mind.
- Volatility indicators (flash point, weight loss tendencies, and similar screening data)
- Lot-to-lot consistency and documentation
- Prior use in automotive interior applications where fogging control is required
Eliminate Automotive Fogging: Make Renkert Oil Your Primary Process Oil Supplier
When customers call us about processing problems like fogging failures, we don’t just “quote a product.”
We help you narrow the variables, compare specialty oil options that fit your specs, and move fast on sampling so you can meet automotive requirements with fewer surprises.
If you’re troubleshooting a TPE fogging issue (or you want to prevent one), reach out to Renkert Oil. As your process oil supplier, we can help you evaluate your current specialty oil choice and build a path to more reliable compliance with interior fogging requirements.
To get started, request a consultation here.
Renkert Oil Is a Proud Sponsor of ILMA Engage 2026
We’re proud to sponsor ILMA Engage 2026 as the Lanyards Sponsor! Taking place April 22–24 at the Hyatt Regency Coconut Point in Bonita Springs, Florida, ILMA Engage brings the lubricants industry together to connect, collaborate, and move the industry forward. We’re excited to support this incredible event and look forward to seeing everyone there.
Learn more at www.ILMAEngage.org.
FAQs: Automotive Interior Fogging from TPE Compounds
- What is automotive “fogging” in interior materials?
Fogging is the film that can form on the inside of a windshield or other glass when volatile compounds migrate out of interior materials and condense on cooler surfaces. - Why do automotive OEMs care so much about fogging?
Because fogging can obstruct visibility and create a noticeable quality issue for drivers, even if the part itself still seems to perform fine. - What does it mean if our TPE “fails” a fogging requirement?
It means your material measured above the fogging limit in the customer’s test method, which can trigger rework, a spec review, or a request to change materials. - Why can a TPE compound process normally but still fail fogging later?
Because fogging is often driven by heat-related volatility over time. The part may run smoothly on the line, but the end-use test can reveal outgassing that only shows up after exposure to heat. - What are the most common causes of fogging in TPE interior components?
Common contributors include volatile ingredients in the formulation, changes in specialty oil selection, lower molecular weight polymer, additive package changes, processing temperature or residence time shifts, and storage conditions for pellets or finished parts. - How can the specialty oil affect fogging performance?
If the specialty oil has higher volatility for the application, more of it can migrate or “boil off” under heat, increasing the likelihood of condensation on glass in fogging tests. - What properties should we look at when choosing a specialty oil to reduce fogging?
A practical starting point is targeting lower volatility, which is often supported by indicators like higher flash point and higher molecular weight, plus consistent documentation and lot-to-lot control. - What is Chevron ParaLux 6001, and why is it used for low-fogging applications?
Chevron ParaLux 6001 is a specialty oil commonly used in automotive interior applications where fogging needs to be minimized. Its higher flash point and higher molecular weight help reduce volatility. An added benefit is that its low color and high stability mean that lighter color match options can be achieved. - Do we need to run our own testing before switching specialty oils?
Yes. Fogging results depend on the full system (polymer + specialty oil + additives + process conditions), so validation testing in your own formulation and process is the safest way to confirm improvement.
- How can a process oil supplier help when we’re troubleshooting fogging?
A process oil supplier can help you narrow variables, review recent changes, compare specialty oil options that fit your specs, and move quickly on sampling so you can reduce risk and meet interior requirements with fewer surprises.