Fuel mix 20:1 or 50:1

[BradSt]

A four stroke only fires and makes power every other rotation, therefore it takes a motor with nearly twice the displacement to produce the same power as a two-stroke

When talking about expansion chamber equipped 2 strokes, this is pretty much the case, but not 0PE that just has a muffler at the exhaust port. That exhaust setup severely limits a 2 strokes output (I know you know this, and this isn't directed at you)

Take these 2 trimmers for example...the FS91 4 mix and the FS94 2 stroke...basically the same power output, with the edge to the FS91. The FS91 is only 10% larger in displacement. The 4 mix trimmer does weigh about 20% more though, and you will eventually have to lash the valves.

The 4 mix was developed years ago, when Stihl thought they were going to have a hard time meeting emissions requirements with their traditional 2 strokes (before they implemented strato designs). I'm pretty sure they licensed tech from Zenoah to produce some of their strato 2 strokes, and they're obviously meeting EPA requirements. IMO, they kept the 4 mix because they spent a lot on R&D, and they were working well and have been widely adopted. The 4 mix BR800 is one of the top dogs in backpack blowers. Significantly lower fuel consumption than the equivalent Echo 2 stroke. I believe that is their only new 4 mix engine in years.

 

[ironman_gq]

Shindaiwa has a very similar 4-mix style engine in their trimmers as well. I have one of each and they're both beasts, easy on fuel, not noticeably heavier than the equivalent 2-strokes if you have your harness setup right, more torque than the 2 strokes. They also seem to run cleaner, less exhaust odor for sure.

 

[Ol' Brian]

All I can advise to you is, Don't knock a 4-Mix ifyou haven't tried one.

I was an EXTREME skeptic too when I bought my first one... to the point the dealer said if you don't like it bring it back. By 10 minutes into using it, I was hooked. Now I won't give it up. I think I said earlier, my first one is either first or 2nd year production for them, and it is still going strong. They probably burn 1/3 less fuel than a comparable 2 stroke... they have the same size fuel tank. On the older 2 strokes, when you ran out of gas, it was about time for a break anyway. With a 4-Mix, when it's time for a break, you've still got half a dang tank left it always seems! By the time you run a full tank through it you're REALLY ready for a break.

 

[bwalker]

No one disputes the power a 4mix makes. As it pertains to blowers they are not significantly more fuel efficient than a redmax or Husky strato charged models of similar capabilities. And with the strato two strokes no valves to adjust or valves to foul which is an issue.

 

[BradSt]

No one disputes the power a 4mix makes. As it pertains to blowers they are not significantly more fuel efficient than a redmax or Husky strato charged models of similar capabilities. And with the strato two strokes no valves to adjust or valves to foul which is an issue.

According to independent lab testing, RedMax EBZ7500/Husky 570 uses 20% more fuel than the Stihl BR700. Echo PB-8010 uses 35% more fuel than a Stihl BR800. Some local lawn service guys seem to report similar real world numbers. 90% of lawn services around here use the BR600 and the EBZ7500 for daily cleanups.

FWIW, I own an EBZ7500.

 

[bwalker]

I'd gladly deal with 20% less fuel economy so I don't have to deal with valves.
I previously owned a Redmax 8000 and now a Husky 580.

 

[Ol' Brian]

I've done the valves on my 4-Mix. Ain't no big deal. Feeler guage, wrench, maybe a screwdriver, plus the torx to get the cover off. 15 min procedure, tops. It's Easy. I need to do them again this Spring. Last time I did them was probaby 3 years ago or so...maybe longer than that. There's been a lot of gas and string and polycut blades through it since then.

Funny thing though... it will not run with the valve cover off.

 

[hseII]

According to independent lab testing, RedMax EBZ7500/Husky 570 uses 20% more fuel than the Stihl BR700. Echo PB-8010 uses 35% more fuel than a Stihl BR800. Some local lawn service guys seem to report similar real world numbers. 90% of lawn services around here use the BR600 and the EBZ7500 for daily cleanups.

FWIW, I own an EBZ7500.

I’ve got a PB-8010.

I’ll keep my 8010 & I’ll keep pouring 36:1 Red Armor same as my saws.


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[HuskyP]

I recently pull the muffler and plug on a 395xp that I was running on 25:1. I was running it at high engine temperatures and for long periods. The saw as tuned wonderfully. No smoke, nice idle, and amazing strong and consistent RPM in the cut (no 4 stroking). When I pull the muffler I noticed some carbon build up on exhaust port and on the top of the piston. The piston walls were beautiful. But the carbon worried me. I then pulled the plug. It was a bit too dark for my liking.

I switched to 50:1, retuned the saw, and cut with a freshly ground chain. The saw runs great. I'd love to hear other's thoughts on this. I figure 50:1 is good enough. Also, I'm done over thinking this stuff. As long as it runs well and I don't see piston scuffing and carbon build-up, I don't really care what the fuel ratio is. I feel the same about chains. As long as they produce nice long chips, I don't care how they are sharpened. Does it cut? Does it run good? Good is good enough for me. I'm more worried about kickback, tension and compression, and all the crazy stuff that happens when falling trees and bucking big wood. Cuts and broken ribs suck, and I've had both.

 

[HuskyP]

I have first hand experience pulling some saws apart after running a rich mix (20:1 or 25:1). You can get a lot of carbon build up on the top of the piston, on the exhaust port, and inside the muffler. Be careful with a rich mix. Modern 2-stroke oils are so good you really don't need more than 50:1. Focus on tuning the saw right, not cutting your feet off, and avoiding kickback. Those things are more important than the mix ratio. Follow the manufacture instructions. Keep it simple. Life is better that way.

Blessings!

I picked up a used, near new condition Stihl HT-131 (4-mix engine) pole saw for $200, yesterday. I was discussing fuel mix with the previous owner and he was telling me that he likes to use 20:1. Stihl specifies 50:1 and it goes against my grain to deviate from manufacturer's engineering specifications.

I checked the plug in the machine and there is no fouling.

My (probably stupid) question is; aside from fouling, what are the downsides of running such an oil rich mixture? I expect the engine would not achieve peak performance and that starting would be more difficult? Having never deviated from fuel mix specs, I would appreciate comments from anyone who has first hand experience with this type of situation.

Thanks.

 

[bwalker]

I recently pull the muffler and plug on a 395xp that I was running on 25:1. I was running it at high engine temperatures and for long periods. The saw as tuned wonderfully. No smoke, nice idle, and amazing strong and consistent RPM in the cut (no 4 stroking). When I pull the muffler I noticed some carbon build up on exhaust port and on the top of the piston. The piston walls were beautiful. But the carbon worried me. I then pulled the

I recently pull the muffler and plug on a 395xp that I was running on 25:1. I was running it at high engine temperatures and for long periods. The saw as tuned wonderfully. No smoke, nice idle, and amazing strong and consistent RPM in the cut (no 4 stroking). When I pull the muffler I noticed some carbon build up on exhaust port and on the top of the piston. The piston walls were beautiful. But the carbon worried me. I then pulled the plug. It was a bit too dark for my liking.

I switched to 50:1, retuned the saw, and cut with a freshly ground chain. The saw runs great. I'd love to hear other's thoughts on this. I figure 50:1 is good enough. Also, I'm done over thinking this stuff. As long as it runs well and I don't see piston scuffing and carbon build-up, I don't really care what the fuel ratio is. I feel the same about chains. As long as they produce nice long chips, I don't care how they are sharpened. Does it cut? Does it run good? Good is good enough for me. I'm more worried about kickback, tension and compression, and all the crazy stuff that happens when falling trees and bucking big wood. Cuts and broken ribs suck, and I've had both.

All engines produce carbon. Even four cycles. How much is as dependent on fuel type, fuel to air ratio and oil type as it is oil ratio..keep this in mind.
I see no reason to run 25:1 in a saw unless you are really heavily loaded. Something like milling large dried oak or locust.
For every day cutting 32:1 -50:1 works fine. In your case a 395 has a good reputation for reliability so you would be ok with a 50:1 ratio of a good quality air cooled oil.
Myself, I run 32:1 in everything because I have been doing it for years in OPE, bikes, sleds, etc and have had very good luck. Clean engines and zero oil related failures.
If your concerned with 50:1 how about splitting the differance and running 40:1?

 

[hseII]

I have first hand experience pulling some saws apart after running a rich mix (20:1 or 25:1). You can get a lot of carbon build up on the top of the piston, on the exhaust port, and inside the muffler. Be careful with a rich mix. Modern 2-stroke oils are so good you really don't need more than 50:1. Focus on tuning the saw right, not cutting your feet off, and avoiding kickback. Those things are more important than the mix ratio. Follow the manufacture instructions. Keep it simple. Life is better that way.

Blessings!

No


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[HuskyP]

No


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I love it. A brief explanation of your opinion....No.... Nuff said. But, if I may ask, "No" to what? I mean that in good spirits. To each his own, my friend. No hard feelings here. I would just like to hear your opinions. Maybe I have some stuff I need to learn.

 

[HuskyP]

All engines produce carbon. Even four cycles. How much is as dependent on fuel type, fuel to air ratio and oil type as it is oil ratio..keep this in mind.
I see no reason to run 25:1 in a saw unless you are really heavily loaded. Something like milling large dried oak or locust.
For every day cutting 32:1 -50:1 works fine. In your case a 395 has a good reputation for reliability so you would be ok with a 50:1 ratio of a good quality air cooled oil.
Myself, I run 32:1 in everything because I have been doing it for years in ***, bikes, sleds, etc and have had very good luck. Clean engines and zero oil related failures.
If your concerned with 50:1 how about splitting the differance and running 40:1?

I like the idea of splitting the difference with 40:1! I'm always open to hearing a different opinion and learning. My experience is mine, and as such is always limited. Thanks for the suggestions!

 

[HuskyP]

So, what does everyone think the best fuel ratio is for a 395xp for making firewood?

That's a wicked question. I can't wait to hear your answers!

 

[lone wolf]

So, what does everyone think the best fuel ratio is for a 395xp for making firewood?

That's a wicked question. I can't wait to hear your answers!

40 to 1 is what i run in all the saws. None burned up .

 

[HuskyP]

40 to 1 is what i run in all the saws. None burned up .

Thanks so much! I will try 40:1

 

[stihl86]

To the OP. You know how it runs and the power band. As for the oil, you want to run a semi or full synthetic oil
@ 50 : 1
Its not so much a problem with the hand helds ( like yours) but on a
BR series bac pac, the carbon will build up and cause a valve leak.
The hand held items are used at various speeds to help keep them clean.
Which oil to use, everybody’s favorite is the best. You like Stihl? Use that.
Any rated air cooled 2 cycle oil will do. IMO
As long as it semi or full.
The engine is going to sound like it’s missing at hi idle.
Do not adjust it out. The ign has a rev limiter.
It’ll clear under load. Sounds like you got a great deal.
Well over 600.00 new. Good luck.

 

[sbhooper]

Why do people insist on running a different mix, than what the book calls for? JUST RUN THE CORRECT MIX! Not even a discussion worth having.

 

[HuskyP]

Why do people insist on running a different mix, than what the book calls for? JUST RUN THE CORRECT MIX! Not even a discussion worth having.

I’m so tired of worrying about this. I decided today that I’m doing what the manual says. I’ve hotrodded a few saws, they all do good at 50:1. Tried something different with the 395. Back to 50:1. That’s