I saw that Autolite offers an iridium plug for the Stihl FS-38 which I've had for five years. It's been the best trimmer I've ever owned. Does anyone have any experience using an iridium plug on 2-stroke ope? I use high octane gas and or avgas.
Iridium plug for stihl trimmer?
- Thread starter 97prizm
- Start date
The iridium is worth trying 
I don't have any 2-stroke experience, but I'd try it. I don't see any disadvantages.
I don't have any 2-stroke experience, but I'd try it. I don't see any disadvantages.
You use avgas in a trimmer with exhaust right next to your mouth and nose?
It won't make any difference compared to a standard copper plug of the same heat range except maybe it will last longer.
I put them in my X320 JD lawn tractor last year.
Easier starting & seems to run better.
I haven't tried them in a 2-stroke yet, but I'll add that to my bucket list of things to do.
Easier starting & seems to run better.
I haven't tried them in a 2-stroke yet, but I'll add that to my bucket list of things to do.
I agree. It's worth trying on any 2-stroke. Even if it doesn't improve anything, what are you out? The difference in price between a standard copper core, and the Iridium, on 1 single spark plug.... Hardly a great loss worth whining about.The iridium is worth trying
I don't have any 2-stroke experience, but I'd try it. I don't see any disadvantages.
I'd like to hear how the Av Gas works in a 2 stroke.
I don't see how it would make a difference either way. 100-LL Avgas has 100 octane, that is achieved by introducing large amounts of Tetraethyl Lead into it. (There is nothing "low" about the amount of lead in, "low lead" Avgas).
That's pretty much how high octane, leaded "Ethyl", (now commonly referred to as "Premium"), was in the 60's before we went to unleaded motor fuels.
Leaded fuel fouled plugs faster, and 2-stroke engines foul plugs fast enough as it is. My guess is that today's 2-stroke engines would run better on unleaded, non Ethanol Premium, (mixed with the proper amount of 2- cycle oil), than they would on 100-LL Avgas.
You could try it, see if it helps with starting. All the Stihl equipment I've owned seemed to be a bear to start even when brand new. I also would echo the other posts and stop buying AvGas, it really has zero advantages in power equipment.
I would run an NGK copper core plug. You can get non ethanol unleaded fuel at boat marinas or lawn equipment deals etc, that is what I run in all my Stihl stuff and I use the VP 2 stroke oil at 40:1
The benefit that i see from running av gas is that it keeps much longer and isn't hard on carb rubber - I'm not a fuel chemistry expert, but I think it's alkylate based, like Tru Fuel and it's variants. That said like billt460 mentioned, "100 Low Lead" is a misnomer. It has plenty in it and breathing even small amounts is... less than desirable. I strongly recommend you find an alternative.
Not entirely true.
It depends on what you consider "large amounts" of lead. Pre-1975 regular leaded automotive gasoline had the same amount of tetraethyl lead in it (about 2 grams of lead/gal) as 100LL Avgas. Some premium leaded gasoline brands had over twice as much (up to 4.5 grams of lead/gal) but typically about 2.8 grams of lead/gal. It is true that after 1974 the amount of lead in regular leaded gas was gradually reduced to 1 gram of lead/gal by 1988 when the sale of leaded fuel for automobile use was discontinued in the US. FYI, leaded automobile gas is still produced and sold in other parts of the world.
The biggest advantage of using Avgas is it's shelf life. It can last as long as 3-4 years in a vented fuel tank, as long as 10 years in an air-tight metal gas can, and it does not need to be treated with stabilizer. Additionally, it will not varnish with age and cause plugged carburetors and problems with other fuel system components like pump gas will, it simply loses volatility (slowly).
Yes, it will lead-foul a spark plug a little faster, but IMO replacing a spark plug once a year or so is preferable to dealing with constant fuel system problems caused by today's pump gas that goes bad and starts to varnish in a few months (even using stabilizer).
Last edited:
I have twelve modified 2t scooters. I've used iridium plugs in them, but it doesn't make a difference and really not worth the extra cost. Standard NGK's are the way to go.
I'm the heretic here. Just retired a 15 year old Husqvarna after the fuel tank developed an incontinence problem. Sent it off with the OEM Champion sparkler. Ran just fine.
Now that my local airport has mogas 100 octane unleaded I'm planning on going with that in the future. It's only available during business hours and not at the pump like avgas.
For most of us, there are no pump based aviation-grade, zero ethanol, 100 octane unleaded fuels available. Are you near one of the CA airports that is supposed to have GAMU G100UL available by summer 2024?
Yes, GAMI and Swift have products they have developed, and I can't wait to try them.
I'd run the Iridium plug. Does Autolite have a sticker you can put on the engine covers?
I just got a Stihl FS70R trimmer a few weeks ago and I can't wait to get enough hours on it so I can pull maintenance.
I've only used it once. For now, I'm running pre-mixed Tru-Fuel; other than ethanol-free and convenience, I see no advantage to paying +$30/gallon for fuel for something that is run once a week. The +92 octane is rather laughable; maybe that's the only way E0 is available? Perhaps the advantage is cooler combustion?
This thing starts on the first pull, even when stone cold. Hopefully, it stays that way.
I just got a Stihl FS70R trimmer a few weeks ago and I can't wait to get enough hours on it so I can pull maintenance.
I've only used it once. For now, I'm running pre-mixed Tru-Fuel; other than ethanol-free and convenience, I see no advantage to paying +$30/gallon for fuel for something that is run once a week. The +92 octane is rather laughable; maybe that's the only way E0 is available? Perhaps the advantage is cooler combustion?
This thing starts on the first pull, even when stone cold. Hopefully, it stays that way.
