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Material Guide
Choosing between silicone and rubber hose
Silicone gets treated as the upgrade and rubber as the cheap option. That is not what the difference is. Silicone buys you temperature range and gives up oil resistance, and on the wrong application that trade goes badly.
- Silicone is not a general upgrade. It is a high temperature material with poor oil resistance.
- The SAE coolant hose classes are defined by oil resistance, and silicone sits at the bottom of that list.
- Silicone wins on temperature range, cold flexibility, ozone and UV.
- Rubber wins on oil, fuel, abrasion and cost, and nitrile beats silicone outright where oil is present.
- Look for the EC marking on coolant hose. Electrochemical degradation is a real failure mode.
- The layline tells you the type and class. Read it before assuming anything.
The premiseSilicone is a trade, not an upgrade
Silicone is the better hose
Costs more, lasts longer, handles more. Fit silicone anywhere you want an improvement over the rubber that came off.
Silicone is the high temperature option
It buys temperature range and cold flexibility at the cost of oil resistance and abrasion resistance. On an oily application it is the worse choice.
You can see this written into the standards. SAE J20, the coolant system hose specification, sorts materials into classes, and the classes are largely defined by how much oil resistance they offer.
Silicone is Class A, described as high temperature resistant. Nitrile is Class B, high oil resistant. Neoprene is Class C, medium oil resistant. EPDM sits at Class D, low oil resistant with the D-3 variant adding high temperature performance. The standard itself is SAE J20, Coolant System Hoses, which sets out the class table and the type designations in full.
Read that list again and the picture inverts. The material people fit as an upgrade is the one the standard singles out for temperature, not for resilience. Where oil is anywhere near the hose, nitrile beats it comfortably.
Side by sideWhat each one is actually good at
Silicone
Silicon-oxygen backbone rather than a carbon one, which is what gives it the temperature range and the stability at both ends of it.
- Very wide temperature range
- Stays flexible when cold
- Excellent ozone and UV resistance
- Poor with oil and fuel
- Tears and abrades more easily
- Costs more
Rubber
A family rather than one material. Nitrile, neoprene and EPDM each solve different problems, which is the point.
- Nitrile handles oil and fuel well
- Better abrasion and tear resistance
- Considerably cheaper
- Narrower temperature range
- Stiffens in cold weather
- Ozone and UV degrade it faster
Notice that the two lists are close to mirror images. That is the whole decision. Neither material is better; they fail at opposite things.
The detail nobody mentionsElectrochemical degradation
Coolant hose can be destroyed by electricity
Engine cooling systems carry stray electrical currents, and those currents attack the inner tube of a coolant hose from the inside. The hose develops fine cracks in the tube while the cover still looks perfect, then fails without any external warning.
The industry response is a specific electrochemical resistance test, SAE J1684, and hoses that pass carry an EC designation in their marking. Many manufacturers now specify EC-rated hose as standard for exactly this reason.
If you are replacing coolant hose on a modern engine and the original carried an EC marking, the replacement should too. This is not an upsell, it is a different failure mode that a non-EC hose is not built to resist.
It is also a good argument for reading the layline rather than matching on appearance. Two hoses that look identical can be built to different classes with different lives.
Reading itWhat the marking tells you
Coolant hose under SAE J20 carries its designation printed along the cover, typically repeated at intervals. The format is SAE 20RXY followed by the class and the inside diameter, plus the manufacturer's own code.
| Type | What it is |
|---|---|
| 20R1 | Heavy duty, for higher pressure service such as diesel and locomotive engines |
| 20R2 | Heavy duty wire embedded, for high vacuum and forced curvature |
| 20R3 | Heater hose, normal automotive service |
| 20R4 | Radiator hose, normal service, optionally wire reinforced against vacuum collapse |
| 20R5 | Convoluted wire supported universal hose |
So a marking reading 20R3 with a class designation tells you it is heater hose and which material family it belongs to. That is considerably more useful than knowing whether it feels like silicone.
Temperature ranges and pressure ratings vary by manufacturer and by grade within each class, so a generic figure is worth very little. What the class gives you is the shape of the compromise. For the actual numbers, use the specification for the specific product.
ChoosingWhere each one belongs
Silicone earns its price
- Turbo and charge air pipework, where intake temperatures are high and the medium is air rather than oil.
- High temperature coolant and heater routing, particularly where a hose passes close to a manifold or turbo housing.
- Anything living outdoors, because ozone and UV are what kill rubber in the open.
- Cold storage and winter equipment, where rubber goes rigid and silicone does not.
- Show and performance builds, where the appearance is genuinely part of the brief.
Rubber is the right answer
- Anywhere oil or fuel touches the hose, inside or out. Nitrile, not silicone.
- Abrasive service, where the hose drags, rubs or takes impact.
- General coolant work on engines that never see extreme temperature, where EPDM does the job at a fraction of the cost.
- High volume replacement, where the cost difference multiplied across a fleet is real money for no gain.
Silicone fitted in an engine bay where oil mist settles on everything. The hose is fine on temperature, holds pressure, and slowly swells and softens from the outside in because of what is landing on it. If there is oil in the environment, that is a nitrile job.
Fitting itSilicone needs different clamps
Silicone behaves differently under a clamp and installing it like rubber causes problems.
- Use constant tension clamps. Silicone relaxes after fitting and moves more with temperature, so a fixed clamp that was correct when cold is loose when hot.
- Spread the load. T-bolt clamps rather than narrow worm gear, because silicone is soft and a narrow band cuts a groove into it. See choosing the right clamp.
- Re-check after a heat cycle. Run the engine to temperature, let it cool, then check the clamps again. This one step prevents most silicone leaks.
- Keep it off sharp edges. Silicone's weak point is tearing, and a cover nick becomes a split.
- Do not over-tighten. The bulge either side of the band means you have gone past sealing and into damaging.
At the counterWhat we carry
We stock silicone coolant and heater hose alongside a full rubber range, and we will tell you which one your job wants rather than which one costs more.
- Silicone coolant and heater hose in the common bores, straight and shaped. See silicone coolant and heater hoses.
- Rubber hose products across nitrile, EPDM and neoprene for oil, coolant and general service. See rubber hose products.
- Braided lines for performance work, where the application genuinely calls for it. See high performance hoses.
- T-bolt and constant tension clamps to fit silicone properly. See hose accessories and fittings.
Bring the old hose or an offcut. The layline usually tells us the type and class, and if it has worn off, the construction and where it came off the engine narrow it quickly. More on custom hose fabrication.
Proudly serving Long Island since 1964
Sixty years supplying coolant, heater and performance hose to Long Island shops, restorers and fleets, from our counters in Nassau County and Suffolk County.
There is a reason people bring the old hose to a counter. Research into near-me search behaviour found that roughly 76 percent of people who run a "near me" search visit a business within 24 hours, citing Think with Google. A car stripped down in the driveway is a today problem.
Common Questions
Silicone and rubber hose FAQ
Not generally, no. Silicone offers a wider temperature range, better cold flexibility and much better ozone and UV resistance. It gives up oil resistance and abrasion resistance to get there. SAE J20 classes silicone as Class A, high temperature resistant, while nitrile is Class B, high oil resistant. Which is better depends entirely on the application.
No. Silicone swells and softens on contact with petroleum products. That applies to oil landing on the outside of the hose as well as anything running through it, which is why silicone in an oily engine bay can fail even when the medium inside is only coolant. For oil and fuel, nitrile is the material.
It designates electrochemical resistance, tested to SAE J1684. Stray electrical currents in an engine cooling system attack the inner tube, producing fine cracks while the cover still looks perfect. EC-rated hose is built to resist that. If the original carried an EC marking, the replacement should too.
They identify the material family and, largely, its oil resistance. Class A is silicone, high temperature resistant. Class B is nitrile, high oil resistant. Class C is neoprene, medium oil resistant. Class D covers EPDM variants with low oil resistance, D-3 adding high temperature performance.
20R3 is heater hose for normal automotive service. 20R4 is radiator hose for normal service, optionally wire reinforced where vacuum collapse is a concern. 20R1 and 20R2 are heavy duty types and 20R5 is convoluted wire supported universal hose.
Yes. Use constant tension or T-bolt clamps rather than narrow worm gear. Silicone is soft, so a narrow band cuts a groove into it, and it relaxes after fitting and moves more with temperature, so a clamp correct when cold can be loose when hot. Re-check after one heat cycle.
Where the application actually needs its properties, yes. High intake temperatures, hose routed near a turbo or manifold, outdoor exposure to ozone and UV, or equipment worked in the cold. Where the job is ordinary coolant duty on an engine that never sees extreme temperature, EPDM does the same work for considerably less.
Read the layline printed along the cover. Coolant hose under SAE J20 carries a designation such as 20R3 or 20R4 with the class and the bore size. If the printing has worn off, bring an offcut in and the construction plus where it came off the engine usually identifies it.
Ask The Counter
Silicone or not?
Tell us the application, the temperature and whether oil is anywhere near it. We will tell you which material the job actually wants, including when the answer is the cheaper one.
Both On The Shelf
The right material, not the dearer one
Silicone coolant and heater hose alongside a full rubber range. Two Long Island counters, six days a week.