# Silicone grease

**Silicone grease** is a lubricating and sealing grease made by thickening a silicone oil, most often polydimethylsiloxane (PDMS), with a solid thickener such as fumed silica, PTFE, or a lithium soap. It is valued for a wide service-temperature range, strong water repellency, chemical inertness, electrical insulating (dielectric) behavior, and compatibility with many plastics and elastomers, and it is sold for plumbing, electrical, sealing, vacuum, and food-processing uses.<sup>[1](https://en.silitech.ch/blog/knowledge-center-7/silicone-paste-and-silicone-grease-applications-compatibility-and-selection-44)</sup>

| Key fact | Detail |
|---|---|
| Composition | Silicone base oil (polydimethylsiloxane) plus a thickener; commercial products use inorganic (silica) thickeners, PTFE, or lithium soap and lithium complex thickeners<sup>[2](https://www.tremack.com.my/pdf/4_osk_PI_OKS_1110_110645_EN.pdf)</sup><sup> • </sup><sup>[3](https://www.dupont.com/content/dam/dupont/amer/us/en/Molykote/public/documents/en/MOLYKOTE_PG-21_Silicone_Grease_71-0111F-01.pdf)</sup> |
| Temperature range | Typically about −40 to +200 °C; one product is rated −40 to +250 °C, and FUCHS GLEITMO SIL 525 FG spans −57 to 204 °C<sup>[4](https://asvmultichemie.com/public/admin/uploads/docs/20200928063450_doc_1.pdf)</sup><sup> • </sup><sup>[5](https://fuchs.azureedge.net/us/en/product/product/154375-GLEITMO-SIL-525-FG/)</sup> |
| Electrical behavior | Excellent dielectric (insulating) properties; dielectric grades are applied to spark plug boots and electrical connectors to exclude moisture and prevent voltage leakage<sup>[6](https://www.dupont.com/products/molykote-g-5008-dielectric-grease.html/1000)</sup><sup> • </sup><sup>[7](https://datasheets.tdx.henkel.com/LOCTITE-LB-8423-en_GL.pdf)</sup> |
| Vacuum grades | High-vacuum silicone greases reach vapor pressures of about 10⁻⁶ Torr or lower; Shin-Etsu HIVAC-G is below 10⁻⁶ Torr with total volatile content under 0.3% after 24 h at 150 °C<sup>[8](https://www.innosiltech.com/industrial-grease/shin-etsu-hivac-g-high-vacuum-silicone-grease/)</sup> |
| Elastomer compatibility | Compatible with many rubbers including EPDM, but not with silicone rubber, which swells on contact with silicone oil<sup>[9](https://oringsupplyco.com/blog/o-ring-lubrication-guide/)</sup><sup> • </sup><sup>[10](https://www.parker.com/content/dam/Parker-com/Literature/O-Ring-Division-Literature/ORD-5700.pdf)</sup> |
| Food-grade status | Many products carry NSF H1 registration, the category for lubricants with incidental food contact<sup>[11](https://www.nsf.org/ca/en/food-beverage/commercial-food-equipment/nonfood-compounds-chemical-registration-certification/food-grade-lubricants-iso-21469-certification)</sup> |
| Known weakness | Poor boundary lubrication of steel under high contact stress; NASA guidance states silicone lubricants are not used in modern space applications because they degrade into an abrasive, polymerized product<sup>[12](https://www.abbottaerospace.com/downloads/naca-tn-2788-effects-of-solvents-in-improving-boundary-lubrication-of-steel-by-silicones/)</sup><sup> • </sup><sup>[13](https://standards.nasa.gov/sites/default/files/standards/NASA/B/2022-12-06-NASA-STD-5017B-Approved.pdf)</sup> |

## Composition and physical behavior

The base oil in nearly all silicone greases is polydimethylsiloxane, an organopolysiloxane fluid; patents and technical data sheets also list polymethylphenylsiloxane oils and mixtures for specialty grades.<sup>[14](https://patents.google.com/patent/US6015777A/en)</sup><sup> • </sup><sup>[2](https://www.tremack.com.my/pdf/4_osk_PI_OKS_1110_110645_EN.pdf)</sup> The thickener turns the oil into a stable grease. Common systems include inorganic thickeners such as fumed silica, PTFE (used in MOLYKOTE G-5008 and KHS Seal & Silicone Grease 04), and lithium soap or lithium complex thickeners.<sup>[2](https://www.tremack.com.my/pdf/4_osk_PI_OKS_1110_110645_EN.pdf)</sup><sup> • </sup><sup>[6](https://www.dupont.com/products/molykote-g-5008-dielectric-grease.html/1000)</sup><sup> • </sup><sup>[3](https://www.dupont.com/content/dam/dupont/amer/us/en/Molykote/public/documents/en/MOLYKOTE_PG-21_Silicone_Grease_71-0111F-01.pdf)</sup><sup> • </sup><sup>[15](https://www.khs.com/fileadmin/user_upload/Datenblaetter-Produkte/Consumables/Schmierstoffe/Db_EN_04_KHS_Seal___Silicone_Grease_04.pdf)</sup>

**Properties that follow from the oil.** PDMS gives the grease a wide temperature range with little viscosity change at low temperature, good aging and oxidation stability, water repellency, and electrical insulation.<sup>[1](https://en.silitech.ch/blog/knowledge-center-7/silicone-paste-and-silicone-grease-applications-compatibility-and-selection-44)</sup> Typical commercial products are rated from about −40 °C to +200 °C, with some dielectric and vacuum grades reaching 204 °C to 250 °C at the top end.<sup>[4](https://asvmultichemie.com/public/admin/uploads/docs/20200928063450_doc_1.pdf)</sup><sup> • </sup><sup>[5](https://fuchs.azureedge.net/us/en/product/product/154375-GLEITMO-SIL-525-FG/)</sup> Because the oil does not contain petroleum products, plumber's-grade silicone grease will not melt like ordinary grease and is non-hazardous and odor free in retail formulations.<sup>[16](https://www.oatey.com/products/P_032628406100/hercules-plumbers-silicone-grease)</sup> [Consistency](https://www.edgepedia.org/consistency) is graded on the NLGI scale; for example MOLYKOTE G-5008 is NLGI 2-3 and MOLYKOTE 111 Compound is NLGI 3-4, a stiff, nonmelting compound.<sup>[6](https://www.dupont.com/products/molykote-g-5008-dielectric-grease.html/1000)</sup><sup> • </sup><sup>[17](https://www.dupont.com/products/molykote-111-compound.html)</sup>

## Applications

**Seals, O-rings, and plumbing.** Silicone grease is a standard assembly lubricant for O-rings, seals, and fittings, especially where the grease touches plastics and elastomers.<sup>[1](https://en.silitech.ch/blog/knowledge-center-7/silicone-paste-and-silicone-grease-applications-compatibility-and-selection-44)</sup> Plumber's silicone grease lubricates valve stems, faucets, ballcock linkages, and pump linkages, and prevents corrosion where waterproof grease is needed; faucet manufacturers such as Moen specify a silicone-based grease for cartridges and warn against plumber's-grade grease, silicone sprays, or any lubricant that may contain petroleum.<sup>[16](https://www.oatey.com/products/P_032628406100/hercules-plumbers-silicone-grease)</sup><sup> • </sup><sup>[18](https://solutions.moen.com/FAQ%27s/FAQ%27s-Troubleshooting/General/Handle_is_difficult_to_operate)</sup>

**Electrical and dielectric uses.** [Dielectric](https://www.edgepedia.org/dielectric) silicone grease is intended chiefly for joints between rubber and ceramic or between two rubber surfaces, as found in automotive spark plug boots and electrical connectors.<sup>[6](https://www.dupont.com/products/molykote-g-5008-dielectric-grease.html/1000)</sup> The compound prevents voltage leakage around electrical connectors, keeping a strong spark in high-energy ignition systems, and also prevents spark plug boots from fusing to the plugs.<sup>[7](https://datasheets.tdx.henkel.com/LOCTITE-LB-8423-en_GL.pdf)</sup> Because it is insulating, it belongs around connector bodies and boots for moisture exclusion, not between metal contact surfaces that must conduct.<sup>[19](https://morelic.com/silicone-grease)</sup>

**Vacuum systems.** High-vacuum silicone grease seals ground-glass joints, stopcocks, O-rings, and flanges in laboratory and industrial vacuum equipment. Its defining specification is low vapor pressure, since any outgassing raises chamber pressure and contaminates the process; refined grades such as Shin-Etsu HIVAC-G support vacuums of 10⁻⁶ Torr, and other products are specified at 10⁻⁷ mbar.<sup>[8](https://www.innosiltech.com/industrial-grease/shin-etsu-hivac-g-high-vacuum-silicone-grease/)</sup><sup> • </sup><sup>[20](https://www.taixingpump.com/high-vacuum-silicone-grease-low-vapor-pressure-chemical-resistant-200c)</sup> MOLYKOTE High Vacuum Grease, an NLGI 3-4 translucent white material, is used primarily in sealing vacuum and pressure systems and also lubricates O-rings in binoculars and telescopes, where it prevents fogging of lenses.<sup>[21](https://www.dupont.com/products/molykote-high-vacuum-grease.html)</sup>

**Food processing.** NSF H1 registration designates lubricants for incidental food contact, and many silicone greases carry it, including OKS 1110, GLEITMO SIL 525 FG, and Super Lube Silicone Dielectric and Vacuum Grease.<sup>[11](https://www.nsf.org/ca/en/food-beverage/commercial-food-equipment/nonfood-compounds-chemical-registration-certification/food-grade-lubricants-iso-21469-certification)</sup><sup> • </sup><sup>[2](https://www.tremack.com.my/pdf/4_osk_PI_OKS_1110_110645_EN.pdf)</sup><sup> • </sup><sup>[5](https://fuchs.azureedge.net/us/en/product/product/154375-GLEITMO-SIL-525-FG/)</sup><sup> • </sup><sup>[22](https://hoachatvattu.com/wp-content/uploads/2023/09/Technical_Data_Sheet_Silicone_Dielectric_Vacuum_Grease.pdf)</sup> OKS 1110 also holds drinking-water approvals under the German UBA guideline and French ACS positive lists.<sup>[2](https://www.tremack.com.my/pdf/4_osk_PI_OKS_1110_110645_EN.pdf)</sup>

## Compatibility with elastomers and plastics

Compatibility is a chemistry question, and silicone grease sits in a specific place in it. It is generally compatible with many plastics and elastomers, and it is the recommended lubricant for EPDM seals, where petroleum-based lubricants cause 40 to 80 percent volume swell within hours.<sup>[1](https://en.silitech.ch/blog/knowledge-center-7/silicone-paste-and-silicone-grease-applications-compatibility-and-selection-44)</sup><sup> • </sup><sup>[9](https://oringsupplyco.com/blog/o-ring-lubrication-guide/)</sup> The Parker O-Ring Handbook lists silicone oil and grease as chemically resistant media for silicone rubber, SBR, and polyurethane seals.<sup>[10](https://www.parker.com/content/dam/Parker-com/Literature/O-Ring-Division-Literature/ORD-5700.pdf)</sup>

The notable exception is silicone rubber itself: silicone oil migrates into the rubber and swells it, so silicone grease should not be used on silicone (VMQ) O-rings unless softening is intended.<sup>[10](https://www.parker.com/content/dam/Parker-com/Literature/O-Ring-Division-Literature/ORD-5700.pdf)</sup> Product data sheets carry the same warning; OKS 1110 cautions that plastics based on silicone, such as silicone rubber, can be attacked by silicone grease.<sup>[23](https://www.oks-germany.com/en/products/oks-1110-multi-silicone-grease/)</sup> For silicone rubber seals, practitioners substitute non-silicone synthetic greases or mineral-oil products matched to the elastomer.<sup>[9](https://oringsupplyco.com/blog/o-ring-lubrication-guide/)</sup>

## Limitations

**Metal-to-metal lubrication is the main weakness.** A National Advisory Committee for Aeronautics study of steel lubrication found that the silicone tested was an extremely poor boundary lubricant, which is why solvents were investigated to improve it.<sup>[12](https://www.abbottaerospace.com/downloads/naca-tn-2788-effects-of-solvents-in-improving-boundary-lubrication-of-steel-by-silicones/)</sup> Research on dimethyl silicone in the boundary regime attributes severe adhesive wear to oxidation creating an oxygen-starved contact.<sup>[24](https://www.sciencedirect.com/science/article/pii/0043164894901651)</sup> For loaded cams, preloaded bearings, and other high-contact-stress metal joints, load-bearing greases such as lithium complex or synthetic products are usually more suitable.<sup>[19](https://morelic.com/silicone-grease)</sup>

**Aerospace and precision service.** NASA-STD-5017B, the standard for space lubrication, states that silicone-based lubricants are not used in modern space applications because they quickly degrade into an abrasive, polymerized product with relatively short lifetimes; the two common wet lubricant chemistries there are hydrocarbons and PFPEs.<sup>[13](https://standards.nasa.gov/sites/default/files/standards/NASA/B/2022-12-06-NASA-STD-5017B-Approved.pdf)</sup> In ultra-high-vacuum work, silicone-free hydrocarbon greases such as Apiezon L are also chosen to avoid silicone contamination, since silicone residue is not removed by standard petroleum-based degreasers and can interfere with later coating or bonding steps.<sup>[25](https://www.tedpella.com/vacuum_html/Vacuum_Grease_and_High_Vacuum_Leak_Sealants.aspx)</sup><sup> • </sup><sup>[26](https://siliconchemicals.com/disadvantages-of-silicone-lubricant/)</sup>

## Selection in practice

Manufacturers express the differences between grades through the technical data sheet: base oil viscosity, thickener type, NLGI grade, operating-temperature limits, vapor pressure, and approvals. OKS 1110, for example, is a transparent NLGI 3 grease with a PDMS base oil and inorganic thickener, rated −40 to +200 °C, with oil separation of 0.86 percent in weight after 18 hours at 40 °C and evaporation loss under 2.5 percent after 30 hours at 200 °C.<sup>[2](https://www.tremack.com.my/pdf/4_osk_PI_OKS_1110_110645_EN.pdf)</sup> A silicone compound for valves and sealing, MOLYKOTE 111, uses a silica thickener, spans −40 to 204 °C, and meets water-contact standards including NSF 51, NSF 61, FDA 21 CFR 175.300, and BS6920.<sup>[17](https://www.dupont.com/products/molykote-111-compound.html)</sup><sup> • </sup><sup>[27](https://www.dupont.com/content/dam/dupont/amer/us/en/Molykote/public/documents/en/MOLYKOTE_111_Compound_22-1087P-01.pdf)</sup> Because compatibility, temperature range, and approvals are product-dependent, the data sheet, not the category name, governs selection.<sup>[1](https://en.silitech.ch/blog/knowledge-center-7/silicone-paste-and-silicone-grease-applications-compatibility-and-selection-44)</sup>

## References

1. [Silicone paste vs. silicone grease: difference and application, Silitech](https://en.silitech.ch/blog/knowledge-center-7/silicone-paste-and-silicone-grease-applications-compatibility-and-selection-44)
2. [OKS 1110 Multi-Silicone Grease product information, OKS Spezialschmierstoffe](https://www.tremack.com.my/pdf/4_osk_PI_OKS_1110_110645_EN.pdf)
3. [TDS – MOLYKOTE PG-21 Silicone Grease, DuPont](https://www.dupont.com/content/dam/dupont/amer/us/en/Molykote/public/documents/en/MOLYKOTE_PG-21_Silicone_Grease_71-0111F-01.pdf)
4. [Silicone compound technical property sheet, ASV Multi Chemie](https://asvmultichemie.com/public/admin/uploads/docs/20200928063450_doc_1.pdf)
5. [GLEITMO SIL 525 FG, FUCHS Lubricants](https://fuchs.azureedge.net/us/en/product/product/154375-GLEITMO-SIL-525-FG/)
6. [MOLYKOTE G-5008 Dielectric Grease, DuPont](https://www.dupont.com/products/molykote-g-5008-dielectric-grease.html/1000)
7. [LOCTITE LB 8423 silicone dielectric compound technical data, Henkel](https://datasheets.tdx.henkel.com/LOCTITE-LB-8423-en_GL.pdf)
8. [HIVAC-G high-vacuum silicone grease, Shin-Etsu / INNOSILICONE](https://www.innosiltech.com/industrial-grease/shin-etsu-hivac-g-high-vacuum-silicone-grease/)
9. [O-Ring Lubrication Guide: What to Use and What to Avoid, O-Ring Supply Co.](https://oringsupplyco.com/blog/o-ring-lubrication-guide/)
10. [Parker O-Ring Handbook (ORD 5700), Parker Hannifin](https://www.parker.com/content/dam/Parker-com/Literature/O-Ring-Division-Literature/ORD-5700.pdf)
11. [Food-Grade Lubricants and ISO 21469 Certification, NSF](https://www.nsf.org/ca/en/food-beverage/commercial-food-equipment/nonfood-compounds-chemical-registration-certification/food-grade-lubricants-iso-21469-certification)
12. [NACA TN-2788: Effects of Solvents in Improving Boundary Lubrication of Steel by Silicones](https://www.abbottaerospace.com/downloads/naca-tn-2788-effects-of-solvents-in-improving-boundary-lubrication-of-steel-by-silicones/)
13. [NASA-STD-5017B, Lubrication of Space Mechanisms](https://standards.nasa.gov/sites/default/files/standards/NASA/B/2022-12-06-NASA-STD-5017B-Approved.pdf)
14. [US6015777A: Silicone greases and methods for their production, Google Patents](https://patents.google.com/patent/US6015777A/en)
15. [KHS Seal & Silicone Grease 04 product data, KHS](https://www.khs.com/fileadmin/user_upload/Datenblaetter-Produkte/Consumables/Schmierstoffe/Db_EN_04_KHS_Seal___Silicone_Grease_04.pdf)
16. [Hercules Plumber's Silicone Grease, Oatey](https://www.oatey.com/products/P_032628406100/hercules-plumbers-silicone-grease)
17. [MOLYKOTE 111 Compound, DuPont](https://www.dupont.com/products/molykote-111-compound.html)
18. [Handle is difficult to operate, Moen Solutions](https://solutions.moen.com/FAQ%27s/FAQ%27s-Troubleshooting/General/Handle_is_difficult_to_operate)
19. [Silicone Grease & Lubricant Manufacturer, Morelic](https://morelic.com/silicone-grease)
20. [High Vacuum Silicone Grease, Taixing Pump](https://www.taixingpump.com/high-vacuum-silicone-grease-low-vapor-pressure-chemical-resistant-200c)
21. [MOLYKOTE High Vacuum Grease, DuPont](https://www.dupont.com/products/molykote-high-vacuum-grease.html)
22. [Super Lube Silicone Dielectric and Vacuum Grease technical data sheet, Synco Chemical](https://hoachatvattu.com/wp-content/uploads/2023/09/Technical_Data_Sheet_Silicone_Dielectric_Vacuum_Grease.pdf)
23. [OKS 1110 Multi-Silicone Grease, OKS Spezialschmierstoffe](https://www.oks-germany.com/en/products/oks-1110-multi-silicone-grease/)
24. [The effects of oxygen availability on the lubricating performance of a dimethyl silicone in the boundary regime, Wear (ScienceDirect)](https://www.sciencedirect.com/science/article/pii/0043164894901651)
25. [Vacuum Grease and High Vacuum Leak Sealants, Ted Pella](https://www.tedpella.com/vacuum_html/Vacuum_Grease_and_High_Vacuum_Leak_Sealants.aspx)
26. [What are the disadvantages of silicone lubricant?, Silicon Chemicals](https://siliconchemicals.com/disadvantages-of-silicone-lubricant/)
27. [TDS – MOLYKOTE 111 Compound, DuPont](https://www.dupont.com/content/dam/dupont/amer/us/en/Molykote/public/documents/en/MOLYKOTE_111_Compound_22-1087P-01.pdf)

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*Topic: Encyclopedia › Technology and the built world › Engineering and manufacturing › Materials science and metallurgy › Polymers and organic materials*

*Initially written Sep 17, 2026 · Reviewed: Oct 15, 2026 · Edited: Oct 15, 2026 · Last review: Oct 15, 2026*

*Copyright 2026 EdgeChat AI, a subsidiary of Biostate AI.*

License: Edgepedia Community License 1.0, https://www.edgepedia.org/edgepedia/license