What is the harm of running to rich of an oil mixture?

[stinkbait]

Whether it is synthetic or not? What are the effects?

 

[Deadwood Kid]

lots of smoke and maybe a fouled spark plug possibly.

im sure someone else can elaborate more detailed-like.

 

[Motodeficient]

More oil also means less gas which is a leaner running saw

 

[Patrick62]

More oil also means less gas which is a leaner running saw

That depends on how the carb is adjusted.

I run 'em a touch richer, doesn't foul plugs.

Just what we needed, another oil thread!

 

[stinkbait]

That depends on how the carb is adjusted.

I run 'em a touch richer, doesn't foul plugs.

Just what we needed, another oil thread!

Sorry for starting the thread. I just wanted to know what harm it would cause, if any.

 

[windthrown]

Seems that the potential issues are for more gunked up deposits in the crankcase, more carbon buildup in the combustion chamber, more plug fouling, as well as muffler screens clogging up faster. Also there will be more smoke, which leads to the last three items in my list. I have found that running old dyno premix oil will lead to all four items, even running at 50:1.

Use 100% synthetic at least JASO FC rated (or equivalent if not rated, like Stihl Ultra) and your saw will run far better and last longer, with fewer issues and a lot less smoke. FD is even better. FB will smoke and clog muffler screens and cause more gunk and carbon buildup in your engine. Marine TWC rated oil will cause even more problems in your saws.

 

[wavefreak]

That's the second time I've seen that on these forums and I can't find a way to reconcile that with chemistry. Oil is fuel just as much as gas. It just doesn't burn as easily. Gasoline is more volatile so it atomizes better before it gets to the combustion chamber, but the chemistry is fixed. The max amount of oxygen that can be consumed is a function of the chemical bonds available to be broken . 100% efficiency would reduce every molecule of fuel into carbon dioxide and water. As efficiency goes down you get carbon monoxide, carbon dioxide and water. In reality you get a mishmash of other things because of impurities and additives. But it is still a basic chemical equation. C2H4 + 3O2 -> 2CO2 + 2H2O would be ethane burning. Gasoline and oil are simply more complex hydrocarbons but the basic equation is the same.

So can someone explain to me this "more oil means leaner" thing? It seems to violate basic chemistry.

 

[Motodeficient]

I am not an expert but it makes sense to me. It seems you answered your own question. Not all of the oil is going to burn, some of it does but not all.

Although the ratio of oil is so low that it may not make much of a difference?

 

[windthrown]

So can someone explain to me this "more oil means leaner" thing? It seems to violate basic chemistry.

Yah, I noticed that and was gonna say something. As you say, the oil would not burn as fast, so there would be some minute amount of 'leaner' burning. However, it would be minute, like at the molecular level, and hardly detectable. I think that any effects of running 'gas lean' would be more than offset by the increase in oil lubrication and thus scoring and other harm typical of running lean would be prevented.

Fouling is the biggest issue of using more oil. That's becasue it does not burn as fast, or does not burn completely. It also leaves more deposits in the crankcase before it burns.

 

[Urbicide]

You can get a lot of carbon buildup. If the carbon gets too thick you run the risk of a piece(s) eventually breaking loose and scoring the cylinder wall and piston. This was more of a problem with the old saws that used motor oil as 2-cycle mix in extremely high ratios. It can also plug exhaust ports / mufflers. Keep it cleaned out and the problems are negligible. Plugs need to be cleaned or changed out much more frequently too. The extra smoke will help keep the skeeters away.

 

[howellhandmade]

That's the second time I've seen that on these forums and I can't find a way to reconcile that with chemistry. Oil is fuel just as much as gas. It just doesn't burn as easily. Gasoline is more volatile SNIP

That's it, right there. Oil is fuel, yes, but it takes a different engine. This isn't just a chemical process, it's mechanical as well. The reaction in a gasoline engine has to take place in a certain amount of time at a certain pressure and temperature. If it can, like with gasoline, it does. If it can't, like oil, it doesn't. Now, you can make an engine that generates enough pressure and heat to combust oil and that has a bore/stroke ratio optimized to capture the energy from the slower combustion of the heavier, less volatile fuel. But it's not on your saw.

Also, I expect that 2-stroke mix oils are formulated (within cost parameters) for maximum lubrication and minimum volatility.

Jack

 

[Bowtie]

You can get a lot of carbon buildup. If the carbon gets too thick you run the risk of a piece(s) eventually breaking loose and scoring the cylinder wall and piston. This was more of a problem with the old saws that used motor oil as 2-cycle mix in extremely high ratios. It can also plug exhaust ports / mufflers. Keep it cleaned out and the problems are negligible. Plugs need to be cleaned or changed out much more frequently too. The extra smoke will help keep the skeeters away.

+1. I have rebuilt or junked so many saws from carbon fouling that destroyed the piston, and in some cases the cylinder. Some of these saws had the exhaust port 60% blocked from carbon.

Too rich is not good. Its not that hard to adjust a 2 cycle engine properly. If you cant adjust it right, you shouldnt own it.

 

[BobL]

As well as fouling the engine, running unnecessarily oil rich gives me a headache and because I often mill with my hip or upper leg leaning on the top of the wrap hand, my chaps get filthy from the exhaust positions of modern saws. Don't forget the additives added to suppress smoke and to lube the engine etc are not all burnt and all have to come out somewhere and you're breathing it.

 

[husqvarmit]

Oil burns hotter than gas so i was told. True? That means more carbon deposits. I would check the flash points between the two and judge from that. Oil may have lower flash point but burn hotter than gas. You decide. Correct me If Im wrong

varmit

 

[madmax]

. Marine TWC rated oil will cause even more problems in your saws.

I learned this the hard way. (pretty good 044 on the to do list because of it)

 

[FullCry]

Hey Mr. Chemist you sound like a smart guy and yes all combustion engines take in fuel and air and emit CO + H20.Thats why we see water running out of exhaust pipes and people that don't know think there is something wrong with their vehicle. Combustion engine emission gases(harmful gases),also include NOX, or oxides of Nitrogen, HC, or hydrocarbons, which is just fumes from fuel, and Carbon Monoxide which we all know is a deadly gas if the fumes are breathed in a small space for some time.
On cars there are these really neat emission systems that they have designed to reduce these bad gases to almost nothing now. It takes four or five different systems to do it but it works.

One thing that a lot of old timers think is that the smog equipment robs an engine of horse power. But on Honda's every year the emissions get better and the hp goes up due to advanced technology. Heck a Honda accord V-6 puts out 255hp with all the emission devices and they will run like a scalded foxhound( on crack cocaine chasing a ##### in heat to) and I remember back in the muscle car era that the two barrel three fifty chevy engines ran about the same amount of hp. I will stop my rambling...take care all FullCry

 

[TreePointer]

That's the second time I've seen that on these forums and I can't find a way to reconcile that with chemistry. Oil is fuel just as much as gas. It just doesn't burn as easily. Gasoline is more volatile so it atomizes better before it gets to the combustion chamber, but the chemistry is fixed. The max amount of oxygen that can be consumed is a function of the chemical bonds available to be broken . 100% efficiency would reduce every molecule of fuel into carbon dioxide and water. As efficiency goes down you get carbon monoxide, carbon dioxide and water. In reality you get a mishmash of other things because of impurities and additives. But it is still a basic chemical equation. C2H4 + 3O2 -> 2CO2 + 2H2O would be ethane burning. Gasoline and oil are simply more complex hydrocarbons but the basic equation is the same.

So can someone explain to me this "more oil means leaner" thing? It seems to violate basic chemistry.

C2H4 = ethene
C2H6 = ethane

I'll use your example of ethene.

Say you have a 2 liter combustion chamber on your saw. Assume one liter of air contains just enough O2 to react with and completely consume one liter of ethene. Put pure ethene in your saw's fuel tank, and ideally every ethene molecule is consumed in your combustion reaction with three molecules of O2. In this scenario, the actual ratio of 1:3 (ethene to oxygen) present in the combustion chamber just so happens to match the stoichimetric ratio of 1:3 in your combustion equation.

Next, dump out the fuel tank on your saw. Make a container 70% ethene and 30% mix oil and fill your saw's tank with it. Now, turn on your engine. The combustion chamber still gets its one liter of air, and it gets its one liter of whatever is in the saw's fuel tank. This time there is 30% less ethene reacting with the same amount of O2. The actual ratio of ethene to O2 present in the combustion chamber is no longer 1:3. It is now (0.7):3 and that is "leaner" than what it had been.

Note that the stoichiometric ratio for the combustion of whatever ethene is present in the chamber never changes. The actual ratio of ethene and O2 molecules present in the combustion chamber does change as a result of adding mix oil to the ethene.

NOTE: This assumes that mix oil doesn't combust at all, or the fraction of mix oil that does combust doesn't have the same stoichiometric ratio with O2 as ethene when it combusts.

DISCLAIMER: This is not intended to be a rigorous explanation of an actual reaction.

 

[Cliff R]

The oil "thing" sure gets PLENTY of coverage here.

Since the late 70's I've ran a 40 to 1 ratio mix using on the best oils available in every saw that I own or have owned. Husqvarna or Stihl Premium mix only, no exceptions.

I also run the highest octane pump fuel available, either 92 or 93 octane.

ALL fuel is used up or swapped out after 6 months (MAXIMUM), usually a lot sooner than that.

Each saw gets maintenence when it returns from the woods, which includes blowing it off with compressed air and cleaning/checking the air filter, chain sharpened/tightened, bar nose greased, etc.

They are kept in perfect tune in all weather (this is FAR more important that the oil mix/ratio IMHO).

Chains are kept razor sharp, if they dull in the field the saw is "parked" or sharpened. Chains are "touched-up" at every fuel up and after every outing.

Zero problems with any of the items mentioned. Haven't had a single P/C problem, matter of fact my oldest saw still has so much compression it is difficult to start without a compression release, always been that way.

Never once replaced a spark plug, and seldom even look at them. Since I work on saws here, I see ALL the troubles that were mentioned, and to date I've never had a saw brought in here with P/C troubles, plugged up exhaust, carboned up piston/cylinder, etc, that didn't have evidence of extreme LACK of maintenence, air leak, poorly tuned carburetor, etc. In almost all cases the chains are so dull they might as well have been put on backwards!

Folks, these are machines, they will wear out, and if not properly maintained, their life cycle will be shortened considerably. You are NOT going to extend that life cycle with additional oil added to the fuel, all by itself. I can not tell you if going below apprx 40 to 1 ratio is detrimental to the saws life, never tried it. I can say for certain that without proper maintenence, doesn't matter what ratio you run......Cliff

 

[BobL]

70% ethene and 30% oil is a 2.5:1 mix ratio which makes it a very unrealistic example. How about we stick to realistic ratios?

None of this stuff makes much difference unless you dramatically change operating mix ratios

For example; with 50:1 the gas represents 50/51'ths of the mix, or 98.03% of the mix is gas.
With 40:1 the gas represents 40/41 or 97.56% of the mix
A 0.53% difference in the amount of gas in the mix will not make much difference in terms of leaness. The critical factor in leaness is the "air to mix" ratio - not the "oil to gas" ratio. This has to change by ~5% or more to make a significant difference.
25:1 means gas is 25/26 or 96% is gas

Now look at what else varies the air to fuel mix ratio. The total amount of air getting into the cylinder is influence by the atmospheric pressure which can commonly vary between 1000 to 1020 mb over a few days. This change represents a 2% change in air pressure and means the saw will get ~2% more oxygen at 1020 than 1000 mb.
Does anyone operating at the same elevation read the atmospheric pressure and then retune? - of course not, a stock saw can tolerate at least a +/- 2.5% change in air pressure which corresponds to shifting the mix down from 50:1 to about 25:1.

Even my old dads 2 man saw (Nominally 12:1), could survive with quite a varied mix ratio from ~10:1 to about 15:1 without any problems - and just as well because he used to prepare his mix by eye using dollops and dashes. If not enough smoke was coming out of the saw he would just add another dash to the mix and sometimes even direct to CS fuel tank.

Now completely unrelated is the fact that extra oil provides extra lube which does protect a saw that constantly operates at high RPMs. This is why a slightly lower mix ratio is recommended for example when milling - but the amount it changes the air to gas ratio is trivial.

 

[weimedog]

70% ethene and 30% oil is a 2.5:1 mix ratio which makes it a very unrealistic example. How about we stick to realistic ratios?

None of this stuff makes much difference unless you dramatically change operating mix ratios

For example; with 50:1 the gas represents 50/51'ths of the mix, or 98.03% of the mix is gas.
With 40:1 the gas represents 40/41 or 97.56% of the mix
A 0.53% difference in the amount of gas in the mix will not make much difference in terms of leaness. The critical factor in leaness is the "air to mix" ratio - not the "oil to gas" ratio. This has to change by ~5% or more to make a significant difference.
25:1 means gas is 25/26 or 96% is gas

Now look at what else varies the air to fuel mix ratio. The total amount of air getting into the cylinder is influence by the atmospheric pressure which can commonly vary between 1000 to 1020 mb over a few days. This change represents a 2% change in air pressure and means the saw will get ~2% more oxygen at 1020 than 1000 mb.
Does anyone operating at the same elevation read the atmospheric pressure and then retune? - of course not, a stock saw can tolerate at least a +/- 2.5% change in air pressure which corresponds to shifting the mix down from 50:1 to about 25:1.

Even my old dads 2 man saw (Nominally 12:1), could survive with quite a varied mix ratio from ~10:1 to about 15:1 without any problems - and just as well because he used to prepare his mix by eye using dollops and dashes. If not enough smoke was coming out of the saw he would just add another dash to the mix and sometimes even direct to CS fuel tank.

Now completely unrelated is the fact that extra oil provides extra lube which does protect a saw that constantly operates at high RPMs. This is why a slightly lower mix ratio is recommended for example when milling - but the amount it changes the air to gas ratio is trivial.

Thankyou for putting this into perspective...my old Homelites recommended 16:1. Mosquito fog. I run syntetics (Bel Ray H1R) at 32:1 now.

I have evolved from old Caster Oils (28 & 32:1) to early synthetics, early Bel-Ray, Klotz etc motorcycle racing world at 50:1; to the newer synthetics (The defunct Mobil 1 MX2T & now BelRay H1R) back to 32:1.

Difference? The earlier generation syntetics seemed to form a gummy almost "tar" like residue in the exaust & power valves of the 1980 era 125's and 250's. Running 50:1 was a nice compomise between clean and cool. When BelRay released the H1R product...I could run 38 and even 32:1 without the residue. (On race motorcycles) The "additional" oil (difference between 50 & 32:1) seemed, in my case; to show up in wear parts like rod & wrist pin bearings and pistons. Many additional factors are in play..but it seemed to me the bikes ran slightly cooler and I definitely had nicer looking tear downs as the seasons progressed with the 32:1 mixes on smaller 125's & 38:1 on open bikes. (You might also say my age was a factor!) So...now I run ALL my two strokes, both "vintage" MX bikes and saws; with 32:1. Not going to change anytime soon as my old saws seem to be liking that mix as well.

I'll let other quantify from a scientific perspective, this is just where my situations&experiences over time have led me.