Running 40:1 in a 50:1 world.

[bunnspecial]

Stihl calls 50:1 "lean" - this does not match with your last paragraph, so there appears to be a disconnect in terminology.

It's common to refer to less oil in the mixture as a "lean" mixture and more oil as a "rich" mixture.

With that said, when the fuel gets into the carburetor, the less oil present, the more easily the gasoline vaporizes. That means that low oil mixtures, used with the carburetor adjustments, will result in the engine running richer.

When more oil is added, the gasoline vaporizes less readily. Unless the carburetor is adjusted to account for this, the end result is the air-fuel mixture being leaner.

Despite the higher oil content, leaner air-fuel mixtures will tend to burn hotter and result in hotter cylinder temperatures. It may be counter-intuitive, but that's the case.

Of course, you can adjust the carb to account for this assuming the carb is adjustable. If you go too heavy handed on the oil, you may run out of adjustment and be into the range where you need to rejet to be correct.

So, again, proceed cautiously messing with what the manufacturer recommends.

 

[tchapps88]

I have seen at hardwares where they sell a multi mix or all ratio oil basically its a 40:1 pouch for casual customer

 

[oil pan 4]

It's common to refer to less oil in the mixture as a "lean" mixture and more oil as a "rich" mixture.

With that said, when the fuel gets into the carburetor, the less oil present, the more easily the gasoline vaporizes. That means that low oil mixtures, used with the carburetor adjustments, will result in the engine running richer.

When more oil is added, the gasoline vaporizes less readily. Unless the carburetor is adjusted to account for this, the end result is the air-fuel mixture being leaner.

Despite the higher oil content, leaner air-fuel mixtures will tend to burn hotter and result in hotter cylinder temperatures. It may be counter-intuitive, but that's the case.

Of course, you can adjust the carb to account for this assuming the carb is adjustable. If you go too heavy handed on the oil, you may run out of adjustment and be into the range where you need to rejet to be correct.

So, again, proceed cautiously messing with what the manufacturer recommends.

I can't help but wonder what they would recommend with out being chained to epa regulations.

 

[Cujet]

when the fuel gets into the carburetor, the less oil present, the more easily the gasoline vaporizes. That means that low oil mixtures, used with the carburetor adjustments, will result in the engine running richer.

When more oil is added, the gasoline vaporizes less readily. Unless the carburetor is adjusted to account for this, the end result is the air-fuel mixture being leaner.

Your point is valid in a way, as it is true that when running excessively more oil, like 8 to 1, operation becomes a bit difficult. But at any mixture above 16 to 1, the temperature of the crankcase+cransk/rod/piston underside, and incredible turbulence involved, result in adequate gasoline vaporization.

In fact, many are unaware that the oil separates from the gas to some extent, and this is where "adequate" lubrication comes from.

To be accurate, we must take in to account that when using more oil, there will be less fuel passing through the main jet. Simple dilution here. We adjust by tuning the engine according to the fuel and oil mix in use.

I will state the point again, 32 to 1 is the ratio where our testing shows adequate protection for most engines. The only conditions where more oil reduces wear is at very high RPM, examples include Kart engines, 125cc (or smaller) motocrossers, or 14,000 RPM chainsaws.

 

[Cujet]

Despite the thought that a cloud of blue haze exists around a 32 to 1 weed wacker, that is just not so, when an EG-D oil and proper tuning is involved. There will be no visible smoke, and minimal smell.

None of this nonsense:

 

[97K15004WD]

Your point is valid in a way, as it is true that when running excessively more oil, like 8 to 1, operation becomes a bit difficult. But at any mixture above 16 to 1, the temperature of the crankcase+cransk/rod/piston underside, and incredible turbulence involved, result in adequate gasoline vaporization.

In fact, many are unaware that the oil separates from the gas to some extent, and this is where "adequate" lubrication comes from.

To be accurate, we must take in to account that when using more oil, there will be less fuel passing through the main jet. Simple dilution here. We adjust by tuning the engine according to the fuel and oil mix in use.

I will state the point again, 32 to 1 is the ratio where our testing shows adequate protection for most engines. The only conditions where more oil reduces wear is at very high RPM, examples include Kart engines, 125cc (or smaller) motocrossers, or 14,000 RPM chainsaws.

I have seen it repeatedly when I disassemble and repair small two stroke engines. Some oil has "separated" from the fuel mix and some stays in the crankcase somewhat - therefore providing lubrication for the bottom end and the wiped portion of the cylinder. That is why when I run 32:1 I have no cylinder scuffing or piston transfer onto the cylinder walls.

To Cujet's point, the fuel mixture is tuned for the machine and it's intended use.

On a side note, I was taught "lean" or "rich" was to be used strictly with stoichiometric mixtures:

Air fuel ratio – x-engineer.org

Tutorial on what is the air-fuel mixture, stoichiometric ratio and its influence on the performance of an internal combustion engine

x-engineer.org

However, for gasoline/oil mixtures, I follow Stihl's guidance - which I have already posted in the thread before.

As an example, 50:1 is called "lean", 20:1 is "rich".

 

[andyd]

I got 47 yrs of use from my 1975 Stihl Farm Boss. Stihl wanted you to use their Stihl oil at 40:!. I run cheaper oil at 32:1. The weed wacker and the Mantis want 50:!. But run fine at lower ratio. The Lawnboys spec 32:!. Mix oil used for last decade is a qt of Valvoline universal 2 stroke oil. To keep it fresh I only mix qt batches with E-10 gas. I used to add MMO too.but decided, it was too much.

 

[E150GT]

So. Say I'm using my new edger which calls for 50:1. If I put 32:1 to better protection should I have to retune the carb? I can say that edger runs full tilt when I doing my edges. Can hit some high rpms.
I'll say this though. I had a cheap troy bilt trimmer that I took apart. It always had 50:1 trufuel in it for the last 10 years since new. When I took the engine apart it was oily. It didn't look like it was worn out. This trimmer was giving me trouble and I decided to see if the if maybe there was a spark arrestor clogged. I started to undo the plastic bits and what I didn't know was that held on some plate on the back of the engine. I heard something fall and get lost so I said screw it. And I took it apart. Everything seemed lubed and in good shape.

 

[oil pan 4]

So. Say I'm using my new edger which calls for 50:1. If I put 32:1 to better protection should I have to retune the carb? I can say that edger runs full tilt when I doing my edges. Can hit some high rpms.
I'll say this though. I had a cheap troy bilt trimmer that I took apart. It always had 50:1 trufuel in it for the last 10 years since new. When I took the engine apart it was oily. It didn't look like it was worn out. This trimmer was giving me trouble and I decided to see if the if maybe there was a spark arrestor clogged. I started to undo the plastic bits and what I didn't know was that held on some plate on the back of the engine. I heard something fall and get lost so I said screw it. And I took it apart. Everything seemed lubed and in good shape.

Probably not. Mine were setup for 50:1 and I went to 40:1 no problem. I might retune the carb on my saws on the low side so the engine doesn't load up with oil when it idles for more than a minute.
I'm going to take the tachometer and retune my weed eater to see if I can get more power out of 40:1 vs 50:1 but I don't have to as it's running great with a 50:1 tune.

 

[Fordiesel69]

"Despite the thought that a cloud of blue haze exists around a 32 to 1 weed wacker, that is just not so, when an EG-D oil and proper tuning is involved. There will be no visible smoke, and minimal smell.

None of this nonsense:"

Cujet brings up another point. When I break in a 50:1 engine I run 32:1 and there is no smoke. But depending on the engine, I will get some black ooz out the muffler seams. This occurs for me on smaller equipment and is less likely on the bigger equipment running full throttle.

 

[E150GT]

I already get a good amount of plug fouling at 50:1 on my edger and chainsaw. Guess I'm not running them hard enough ?

 

[oil pan 4]

I already get a good amount of plug fouling at 50:1 on my edger and chainsaw. Guess I'm not running them hard enough ?

Probably running a plug that's 1 or 2 heat ranges too cold.
I ran the factory plug on my redmax weed eater from 2017 to 2022.

 

[userfriendly]

"Despite the thought that a cloud of blue haze exists around a 32 to 1 weed wacker, that is just not so, when an EG-D oil and proper tuning is involved. There will be no visible smoke, and minimal smell.

None of this nonsense:"

Cujet brings up another point. When I break in a 50:1 engine I run 32:1 and there is no smoke. But depending on the engine, I will get some black ooz out the muffler seams. This occurs for me on smaller equipment and is less likely on the bigger equipment running full throttle.

Let’s talk about the black ooze coming out of the exhaust system.
Two stroke pre-mix is obviously not a lubricant as it is definitely not slippery.
So what happens to the gasoline oil blend when it enters the engine.
Does the running engine separate the oil from the gasoline with centrifugal force?
Is the black liquid that drips from two stroke dirt bikes exhaust pipe unburnt oil?

 

[E150GT]

Probably running a plug that's 1 or 2 heat ranges too cold.
I ran the factory plug on my redmax weed eater from 2017 to 2022.

these are brand new engines with factory plugs. Echo SRM-2620 which I admit I need to run harder but right now I am just maintaining the grass as its been so hot so it doesnt grow much. My chainsaw on the other hand Echo CS-400 I was a bit disappointed in. I used it once and it wouldnt start the second time I needed it. The plug was wet and black. It finally started after letting it sit for a day. Im talking a chainsaw that has had maybe on tank run through it. The Echo Edger hasnt had that fouling issue but it does run full blast when I use it. unlike my string trimmer.

 

[jeepman3071]

these are brand new engines with factory plugs. Echo SRM-2620 which I admit I need to run harder but right now I am just maintaining the grass as its been so hot so it doesnt grow much. My chainsaw on the other hand Echo CS-400 I was a bit disappointed in. I used it once and it wouldnt start the second time I needed it. The plug was wet and black. It finally started after letting it sit for a day. Im talking a chainsaw that has had maybe on tank run through it. The Echo Edger hasnt had that fouling issue but it does run full blast when I use it. unlike my string trimmer.

Echo equipment is known to be set rich from the factory, which is probably why they have the longest warranty, since it would be impossible to blow them up from running too lean. With that said, after 10 tanks or so you will notice a big difference in how the saw runs since it will be broken in. I never believed this until I experienced it with my own CS-3510. It was so rich at idle it would stumble and occasionally die if left idling too long. I adjusted it to run better at idle, and after a few tanks I noticed I had to adjust the low speed jet back to where it was and the saw had noticeably more power.

 

[shortyb]

Lots of valid points being made in this thread. Main ones being about fuel content, cooling and oil separation. Just my opinion, but IF you know how to properly tune your carb, you can use ANY fuel ratio you'd like to get whatever result you want, ie; less wear, cooler running, more power etc. If you DON'T know, or try to "bench" it without proper techniques (no tach? no touch), you could end up melting down your nice piece of equipment in short order. I've found different pieces run differently on varying ratios (obviously).

I like the tune method used in my newer stuff where I adjust for highest running rpm at 50:1, then add oil til it shows a drop in revs. Back off oil a tad and thats where it runs. Do a couple plug chops til it looks right and thats where it stays, usually around 45:1 or so. Currently using Red Armor canned 50:1 with additional 1/2oz. per gal. of RA oil. Older stuff gets tuned same way but start with recommended ratios and adjust by ear.

 

[oil pan 4]

Echo equipment is known to be set rich from the factory, which is probably why they have the longest warranty, since it would be impossible to blow them up from running too lean. With that said, after 10 tanks or so you will notice a big difference in how the saw runs since it will be broken in. I never believed this until I experienced it with my own CS-3510. It was so rich at idle it would stumble and occasionally die if left idling too long. I adjusted it to run better at idle, and after a few tanks I noticed I had to adjust the low speed jet back to where it was and the saw had noticeably more power.

Yeah I had to turn the low side down on mine. They would load up with fuel/oil and stall at the factory setting after idling for more than 3 or 4 minutes.

 

[userfriendly]

Lots of valid points being made in this thread. Main ones being about fuel content, cooling and oil separation. Just my opinion, but IF you know how to properly tune your carb, you can use ANY fuel ratio you'd like to get whatever result you want, ie; less wear, cooler running, more power etc. If you DON'T know, or try to "bench" it without proper techniques (no tach? no touch), you could end up melting down your nice piece of equipment in short order. I've found different pieces run differently on varying ratios (obviously).

I like the tune method used in my newer stuff where I adjust for highest running rpm at 50:1, then add oil til it shows a drop in revs. Back off oil a tad and thats where it runs. Do a couple plug chops til it looks right and thats where it stays, usually around 45:1 or so. Currently using Red Armor canned 50:1 with additional 1/2oz. per gal. of RA oil. Older stuff gets tuned same way but start with recommended ratios and adjust by ear.

Do you have any experience with Husqvarna’s auto tune?

 

[kschachn]

So what happens to the gasoline oil blend when it enters the engine.
Does the running engine separate the oil from the gasoline with centrifugal force?

You cannot separate two miscible fluids with a centrifuge. Solutions don’t separate due to gravity.

 

[shortyb]

Do you have any experience with Husqvarna’s auto tune?

No, however I have 2 Husky products that are tuned as above and run like scalded dogs.