Stihl 4-mix engine oil

[SteveSr]

The advice you have given is perfect for an air cooled two cycle, but poor for a 4mix.
The 4mix is a terrible design and really runs longer before valve adjustments/issues with an ashless oil. Which is why Stihl had Ultra formulated they way it is.
I'd be inclined to stick with Ultra to be honest.

I won't debate the 4-mix design. Actually I wouldn't care about valve adjustment interval issues. I would be more concerned with carbon deposits. Am I wrong in thinking that an FD oil would be better in trying to clean up this mess than an FB oil like Ultra?

 

[Vintage Engine Repairs]

The issue here is you’re using an oil designed for racing in very low load, low rpm application and expecting it to burn cleanly. Dominators job is to keep a race engine that runs on the very edge of its capability lasting (for a relatively short period) under extreme conditions before being disassembled, cleaned and rebuilt. Some have success in saws because they tend to be under much higher loads for longer periods, but this isn’t what is commonly seen with weed eaters, especially 4 mixes at that.

I’d suggest you use an oil designed for garden power tools.

Edit: This is how dominator is designed to be used - listen to the engine, it will hopefully drill it home that it’s not for OP3… these engines will run like this for about 10-20 hours with how this guy is riding before teardown and rebuilds, that can be stretched to 60 or so if it’s not ridden so hard. OP3 with the right oil will last thousands

 

[huskihl]

Dominator in reality is cleaner than Saber.

That’s been my experience in chainsaws. I also have an echo blower and strimmer I could remove the muffs and check. All they’ve been run on is Dom 32:1

 

[huskihl]

I run saber in all my machines like that never had on gum up. Usually the carbs go bad though. OP waht ratio oil oil and are you running it at low RPM a lot?

I’ve used Dominator for a few years and never seen any buildup in my saws. Only carbon is a black swirl on the piston

 

[lone wolf]

I’ve used Dominator for a few years and never seen any buildup in my saws. Only carbon is a black swirl on the piston

Its loading up from low RPMs.

 

[lone wolf]

Pull the muffler and look at the exhaust port for accumulated carbon. While you are at it you can pull the spark screen off the muffler and burn it clean with a torch.

The gold standard is the conventional 4-stroke leakdown test to see how much the valves are leaking.


What are the ratings? JASO F?


At this point you likely have an engine full of carbon which Ultra won't (actually can't) clean up. Your best bet is to use an FD rated oil and clean as much carbon out of the exhaust port and muffler as possible.

I think that the screen in the muffler clogging would start this whole event yes. But low RPM is the culprit.

 

[bwalker]

I won't debate the 4-mix design. Actually I wouldn't care about valve adjustment interval issues. I would be more concerned with carbon deposits. Am I wrong in thinking that an FD oil would be better in trying to clean up this mess than an FB oil like Ultra?

The deposits are what causes the valves to need adjustment.
And yes you would be wrong.
The mettalic detergents used in FD oils build up on the valves and seats and this is where the valve problems start.

 

[bwalker]

Pull the muffler and look at the exhaust port for accumulated carbon. While you are at it you can pull the spark screen off the muffler and burn it clean with a torch.

The gold standard is the conventional 4-stroke leakdown test to see how much the valves are leaking.


What are the ratings? JASO F?


At this point you likely have an engine full of carbon which Ultra won't (actually can't) clean up. Your best bet is to use an FD rated oil and clean as much carbon out of the exhaust port and muffler as possible.

Mobil MX2T/2R was a ISO EGD/ FD oil.
Once deposits are present in a engine they typicly stay there. I've never seen an oil clean existing deposits and not from lack of looking. Running pig rich will tend to gradually remove deposits from the piston, but often make deposits in the muffler and exhaust port worse.
And Stihl designed Ultra as an ashless oil specifically with the 4mix in mind. I would stick with Ultra in a 4mix or better yet not buy one of those abortions in the first place.

 

[wildwes]

better yet not buy one of those abortions in the first place

I 100% agree with this

 

[bwalker]

I 100% agree with this

I mean it takes the bad points of both engines and combines them. No upside at all.

 

[sundance]

I mean it takes the bad points of both engines and combines them. No upside at all.

Only upside I see is I already own it, have for many years.
Would i buy another? Likely not.

 

[Lionsfan]

Only upside I see is I already own it, have for many years.
Would i buy another? Likely not.

Exactly. Mine runs, everytime I pull the cord and does what it's supposed to do.

 

[sundance]

Exactly. Mine runs, everytime I pull the cord and does what it's supposed to do.

Mine did for a long time, then it didn't leading to this thread.

 

[Lionsfan]

Mine did for a long time, then it didn't leading to this thread.

When mine pukes, I'll throw it out and move forward, no hard feelings.

 

[sundance]

When mine pukes, I'll throw it out and move forward, no hard feelings.

I'm going to try a fuel change first. If not, reckon I've got my money's worth and I'll be shopping. Not sure which one's to look at however.

 

[SteveSr]

I'm going to try a fuel change first. If not, reckon I've got my money's worth and I'll be shopping. Not sure which one's to look at however.

These are definitely rebuild-able but too labor intensive for a dealer to do it. This sounds like a good rebuild project for this winter. Buy yourself a gasket kit, carb kit, and an impulse line and have at it.

 

[SteveSr]

The deposits are what causes the valves to need adjustment.
And yes you would be wrong.
The mettalic detergents used in FD oils build up on the valves and seats and this is where the valve problems start.

So what are these metallic detergents and what makes them stick to the seats and valves? BTW, carbon appears to do the same thing... sticks to the valves and seats until there isn't enough compression to run.

 

[bwalker]

So what are these metallic detergents and what makes them stick to the seats and valves? BTW, carbon appears to do the same thing... sticks to the valves and seats until there isn't enough compression to run.

Mostly calcium and magnesium based compounds.
Attached is a pic of what they look like. It isn't from a 4mix engine but rather an engine that requires a ashless oil, but was ran with a low ash FC/FD type oil.
These deposits are much harder than carbon and are not scraped off like carbon is when the valves close.

 

[bwalker]

Mine did for a long time, then it didn't leading to this thread.

They all end up in the same place given enough hours. Some faster than others.

 

[bwalker]

When it comes to the types of equipment 4mix engines are used in Redmax or the Husky badged Redmax's are the only way to fly. Way more durable and just as powerful. Echo/Shindaiwa are good too, although Shindaiwa stuff is typicly underpowered.