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Part# 08-01234-12
MFR Model# UREM38S-12PK



Aviation Spark Plug With the most automated manufacturing processes and the most innovative spark plug in the aviation industry. Made in USA.

High Conductivity Copper Core Center Electrode copper, co-extruded inside a nickel alloy sleeve ensures outstanding heat and electrical conductivity while the nickel sleeve offers high resistance to corrosive combustion gases.

High Alumina Ceramic Insulator high mechanical strength, superior dielectric properties, proprietary protective glaze, provides high performance to conquer severe operational conditions. "Clean Collar" massive electrode "V" tip focuses heat to reduce fouling and enhance heat range control.

Proprietary Glass Center Seal 21st century 'fired in' resistor replaces the multipart screw, spring, carbon pile stack up used in competitive plugs and known to suffer from resistance value instability that can cause misfires, wasted fuel, engine roughness.

Nickel Finish environmentally preferable electrolytic nickel provides outstanding durable finish, superior corrosion protection, and extreme wear resistance.

Nickel Ground Electrodes aviation grade nickel electrode design focuses on minimizing sparking voltage requirements while maintaining specification gaps to ensure large, stable 'flame kernels' for on-time ignition and complete combustion.

Vacuum Infused Center Electrode proprietary, vacuum infusion process seals electrode/insulator gap providing stable heat range and superior center electrode cooling (heat flow to the insulator).

Hot-Lock Assembly intense pressure and heat create positive, zero-leakage, shrunk in seal between insulator and shell to contain the hot, high pressure combustion cycle gases.

Harness Wire Contact smooth, uninterrupted, oxide treated spring contact surface offers enhanced corrosion resistance, is chemically bonded to the fired-in resistor providing the ultimate harness/spark plug termination integrity and energy transfer.
California Prop 65 Warning Symbol

WARNING: Cancer and Reproductive Harm -

Application Guide

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After having fowled plugs and so many issues, I received recommendations for these plugs from many pilots. Although I though it was crazy to spend this kind of money for plugs, in the long run it has saved many headaches and reduced the cost of hiring an A & P to keep servicing the old plugs.

Leslie L Verified Purchase


March 10, 2023

Peter T Verified Purchase


May 19, 2022

Yes, these plugs are expensive but hey live up to the hype! I had massive plugs that were always fouling in the bottom position of a couple cylinders. The engine was never smooth because of this. Now with the fine wire plugs the engine purrs. Just wish they were not so expensive

Eaa C
May 11, 2021

They may be spendy, but they last a long time and I have never had one foul. The set that these are replacing lasted for just under 1,100 hours.

Steve R
April 21, 2021

Very pleased with communication with staff and speed of process and delivery Purchased items packed well and received in excellent condition.

Stan O
March 15, 2021

I replaced the bottom four plugs in my Lycoming O-360 and they were an immediate improvement over the older massive electrode plugs. The engine started easier, and there was no detectable fouling which was a frequent problem in the past after engine start. Its a hefty investment, so Ill wait to replace the top plugs, but worth it so far.

Red B
September 28, 2020

Following up on my provisional report of last November (2018), my first removal of the Tempest plugs was recently accomplished, after 34 flight hours of exceptionally smooth, trouble-free operation however, to my great surprise one of the removed plugs was missing its center iridium electrode. This plug was from the bottom position in the number 3 cylinder, and a flashlight inspection of the empty hole revealed the detached electrode, still sitting just above the point where the base of the plug had extended during operation. I immediately notified Tempest Aero Group, and that same day they shipped out eight new plugs, via overnight UPS. I returned the one with the missing electrode, as well as the one that had seemed particularly prone to cross-threading, but was advised to retain the other six as spares - a nice and appreciated touch. Amazingly enough, the missing electrode had caused *no* discernible changes in engine operation, including no difference in EGTs, CHTs and individual magneto drops during pre-flight run-ups - *or* during brief in-flight checks. My guess is that the gap between the remaining portion of the center electrode, and the unaffected side post, was so close to nominal specifications that there was no degradation in performance. The new set still was a bit more challenging to initially engage in the cylinder threads than the Champion iridium plugs had been - the latter occurring over 2,000 flight hours of routine removals and reinstallations - but a surgical touch here and there ultimately resulted in proper seating of all eight new plugs. (Tempest recommends use of its T-556 graphite-based anti-seize product, which I now have on order.)

October 12, 2019

Great product! I have purchased these fine wire plugs before!

September 10, 2019

O-360-A4M - Much smoother idle than the Champion REM40E plugs that I replaced. Noticeably smoother operation in cruise as well. All plugs measured between 1000 and 1500 ohms.

December 6, 2018

engine sounds and runs great. IO-360A1B6 RV-8A

May 25, 2018


Please note, Aircraft Spruce's personnel are not certified aircraft mechanics and can only provide general support and ideas, which should not be relied upon or implemented in lieu of consulting an A&P or other qualified technician. Aircraft Spruce assumes no responsibility or liability for any issue or problem which may arise from any repair, modification or other work done from this knowledge base. Any product eligibility information provided here is based on general application guides and we recommend always referring to your specific aircraft parts manual, the parts manufacturer or consulting with a qualified mechanic.

Q: Which spark plug socket will work with this longer spark plug?

Per our tech: The ATS socket should work fine, part number 12-01693. This is a pretty common size spark plug for aviation engines.

Q: When I add UREM38S to my shopping cart it changes the plug # to UREM38S XL. What does the XL stand for and is the plug longer than the massive plug # UREM38E?

No, XL just denotes that it is an iridium fine wire plug. It is not any longer than the UREM38E and will not rub on your cowling.

Q: Application chart shows 5/8 and 3/4 thread - ordering info for UREM38S doesnt seem to indicate which is shipped. When ordered which plug thread is shipped?

UREM38S is a 5/8"-24 plug. If you order UREM38S, you will get a 5/8"-24 plug.

Q: What size of gasket is used for this Tempest plug UREM38S?

This plug comes with an 18mm copper gasket.

Q: If I change to fine wire plug, do I need to change harness?

No, the harness does not need to be changed when switching to fine wire plugs. If your regular plug is an UREM38E for example, you can make the direct switch to UREM38S.

Q: Can I mix fine wire and massive plugs in an engine? Massive on top fine wire on bottom?

Yes, you can do this. People typically run the fine wires on the bottom if they are having fouling issues.

Q: What gap are these plugs pre-set to?

They are gapped .017"-.021".

Q: We have a Continental IO-550 Turbo engine, in our Cirrus SR22T. What model of Tempest Iridium plugs should we buy?

Per the application guide, which should only be used a reference and it is always best to check the currently installed plugs to determine the replacement, the IO-550 can take the URHB36S or URHB32S.

Q: What is the difference between URHB32S and URHB36S. The specs show 3/4-20 with 13/16 reach. I am researching replacing the massive electrodes for fine wire plugs for a Continental IO470S.

The URHB36S is just a hotter burning plug than the URHB32S. Either can be used on your engine.