---
product_id: 1934494
title: "81878 Ultra Copper Maximum Temperature RTV Silicone Gasket Maker, 3 oz. Tube"
brand: "permatex"
price: "$25.65"
currency: USD
in_stock: true
reviews_count: 13
category: "Permatex"
url: https://www.desertcart.us/products/1934494-81878-ultra-copper-maximum-temperature-rtv-silicone-gasket-maker-3
store_origin: US
region: United States of America
---

# 8x Flexibility Max Temp 700°F 3x Oil Resistant 81878 Ultra Copper Maximum Temperature RTV Silicone Gasket Maker, 3 oz. Tube

**Brand:** permatex
**Price:** $25.65
**Availability:** ✅ In Stock

## Summary

> 🔥 Seal the deal with the ultimate high-temp gasket maker!

## Quick Answers

- **What is this?** 81878 Ultra Copper Maximum Temperature RTV Silicone Gasket Maker, 3 oz. Tube by permatex
- **How much does it cost?** $25.65 with free shipping
- **Is it available?** Yes, in stock and ready to ship
- **Where can I buy it?** [www.desertcart.us](https://www.desertcart.us/products/1934494-81878-ultra-copper-maximum-temperature-rtv-silicone-gasket-maker-3)

## Best For

- permatex enthusiasts

## Why This Product

- Trusted permatex brand quality
- Free international shipping included
- Worldwide delivery with tracking
- 15-day hassle-free returns

## Key Features

- • **Sensor-Safe & Low Odor:** Formulated to be non-corrosive and safe for sensitive engine sensors, with minimal odor for a cleaner workspace.
- • **Flexibility That Adapts:** Eight times more flexible than cut gaskets, maintaining integrity despite vibration and movement.
- • **Superior Oil Resistance:** Three times more resistant to oil than conventional silicones, ensuring long-lasting seals under pressure.
- • **Unmatched Heat Endurance:** Handles extreme temps from -75°F to 700°F intermittent—engineered for high-performance engines.
- • **Universal Fit for Critical Components:** Perfect for exhaust manifolds, valve covers, oil pans, and more—trusted by pros for reliable sealing.

## Overview

Permatex 81878 Ultra Copper RTV Silicone Gasket Maker is a professional-grade, sensor-safe sealant designed for high-performance and turbocharged engines. It offers superior adhesion, exceptional oil resistance, and extreme temperature tolerance from -75°F to 700°F intermittent. Its flexibility and durability make it ideal for exhaust manifolds, valve covers, and other critical engine components, ensuring leak-proof performance and long-lasting reliability.

## Description

Permatex Ultra Copper. For 4-cylinder, turbocharged or high-performance engines. The most advanced, high temperature RTV silicone gasket available. Sensor safe, low odor, noncorrosive. Superior adhesion. 3 times more oil resistant than conventional silicones; 8 times more flexible than cut gaskets. Temperature range -75 deg. F. to 700 deg. F. intermittent; resists auto and shop fluids and vibration. Suggested Applications : Exhaust manifolds/headers, valve covers, oil pans, timing covers, water pumps, thermostat housings. 3 oz tube. Carded.

Review: good value, working well - good brand & product
Review: Good go to - Works great. My badly made NEW rear catalytic converter with a warped flange was leaking and it was giving me a code. Tried several time with different gaskets, but ended up using this silicone and a donut gasket/ Haven't got a code since. Good stuff.

## Features

- Most Advanced, High Temp Rtv Silicone Gasket Available.Fit Type: Universal
- Three Times More Oil Resistant Than Conventional Silicones; Eight Times More Flexible Than Cut Gaskets
- Sensor-Safe, Low Odor, And Non-Corrosive With Superior Adhesion
- Temperature Range -75F To 700F Intermittent

## Technical Specifications

| Specification | Value |
|---------------|-------|
| ASIN | B0002UEOPA |
| Best Sellers Rank | #1,572 in Automotive ( See Top 100 in Automotive ) #4 in Gasket Sealers |
| Brand | Permatex |
| Color | Copper |
| Customer Reviews | 4.7 4.7 out of 5 stars (3,240) |
| Date First Available | June 3, 2025 |
| Exterior | Painted |
| Full Cure Time | 24 Hours |
| Global Trade Identification Number | 00686226818782 |
| Is Discontinued By Manufacturer | Yes |
| Item Form | Paste |
| Item Weight | 3 ounces |
| Item model number | 81878 |
| Liquid Volume | 3000 Milliliters |
| Manufacturer | PERMTX-LOCKT |
| Manufacturer Part Number | 81878 |
| Material | Metal |
| Model | Permatex 81878 |
| National Stock Number | 8030-01-598-1435 |
| Number of Items | 1 |
| OEM Part Number | PMT81878 |
| Product Dimensions | 8 x 4 x 2 inches |
| Special Features | Forms a superior bond on oil contaminated metals and maintains outstanding oil resistance |
| Surface Recommendation | Pipe |
| UPC | 686226818782 |
| Unit Count | 3.0 Ounce |
| Water Resistance Level | Waterproof |

## Product Details

- **Brand:** Permatex
- **Color:** Copper
- **Full Cure Time:** 24 Hours
- **Item Weight:** 85 Grams
- **Liquid Volume:** 3000 Milliliters

## Images

![81878 Ultra Copper Maximum Temperature RTV Silicone Gasket Maker, 3 oz. Tube - Image 1](https://m.media-amazon.com/images/I/81freAdVPGL.jpg)

## Available Options

This product comes in different **Size** options.

## Questions & Answers

**Q: Can this be used on a valve cover gasket to get a better seal?**
A: Yes.  It is better than OEM gaskets in that it conforms to any warpage, dents, dings, & other incongruities, whereas OEM gaskets are designed for factory new, perfect valve covers without flaws.  Withstands 700 degrees.

**Q: Can I use this product to seal several non-moving parts of a wood burning stove instead of the standard gasketing material?**
A: This gasketting goop is absolutely incredible for sealing wood stove parts.  I’d certainly never use it on the fire box.  But it can and will hold to moving parts in high temperatures.  It lasts for several years on one application.

**Q: can I use this to seal radiator tubes to a heat exchanger in my gas furnace? Gaskets no longer available for it.**
A: Greetings! As I don't know this application, specifically, I can say that say that Ultra Copper is excellent for sealing liquid coolant surfaces in truck/auto repairs. Temperature, up to about 800*F and pressures exceeding 15 psi will remain sealed with this product. U.C. remains a pliant sealing silicone "glue", but it won't harden, as epoxy does. If you need a sealer that also hastens, look elsewhere. If this is for a flange or any flat, secured surface, you're good-to-go. NO acetic acid in this product, if that's a plus for you.

**Q: Can I spread this on outside of exhaust manifold leak like you would caulk something or does it have to go between parts?  F150 '04 V8**
A: It is too much pressure and heat to use any caulk or rtv. Even muffler cement doesn't work. You might have a lean fuel mixture to cause the problem in he first place. Exhaust bolts rust solid from heat erosion, use the right amount of points on the socket to get bolts out(6 sided bolt--6 sided socket) Copper metal exhaust gaskets work well. Mr. Gasket brand.

## Customer Reviews

### ⭐⭐⭐⭐⭐ good value, working well
*by S***D on February 2, 2026*

good brand & product

### ⭐⭐⭐⭐⭐ Good go to
*by A***R on February 10, 2026*

Works great. My badly made NEW rear catalytic converter with a warped flange was leaking and it was giving me a code. Tried several time with different gaskets, but ended up using this silicone and a donut gasket/ Haven't got a code since. Good stuff.

### ⭐⭐⭐⭐⭐ The Only RTV for High-Heat Engine Jobs
*by M***N on October 11, 2025*

If you're working on anything high-heat, like an exhaust manifold or turbo application, this is the only gasket maker to use. The Ultra Copper RTV is a workhorse—it handles maximum temperatures without breaking down, shrinking, or leaking. It goes on smoothly, cures quickly, and forms a super durable, tight seal. I've used it on headers where standard RTV would just burn up, and this holds strong. It's the professional choice for reliability under extreme heat. Essential for engine work.

## Frequently Bought Together

- Permatex 81878 Ultra Copper Maximum Temperature RTV Silicone Gasket Maker, 3 oz. Tube
- J-B Weld 37901 ExtremeHeat High Temperature Resistant Metallic Paste - 3 oz
- Permatex 80335 Muffler and Tailpipe Sealer, 3 oz., Plastic, 1 Count (Pack of 1)

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*Product available on Desertcart United States of America*
*Store origin: US*
*Last updated: 2026-03-20*