Two-cycle oil Formulations

I am going to lock this thread for the time being and speak to the other mods about transferring this engine operation discussion to a new thread.
 
I have reopened the thread.

Several posts have been deleted due to violation of BITOG rules.

I implore all to tread carefully; violating our tenets will result in actions taken.
 
As much as I believe that Bwalker is probably right on this as you just gotta be a 2T nut to really grasp or care about any of this... I went back to late 90s and mid 2010s for this article and it's just what he's showing except different layouts at times over the years. The full study appears to have never been published on maximausa.com.
 
Bwalker said:
Boy, thats not it at all.
It started because Mola was unaware that the gasoline and oil seperate inside the crankcase and that liquid gasoline and oil, which has virtually no lubricating capacity is not what lubes the motor. Amongst other things..
You might as well say that everything he has posted in regards to what happens in the motor is false.
Click to expand...


Your first post in this thread was #63, there you replied to Molakule - " The viscosity of the the oil once inside the motor is the viscosity of the oil prior to mixing with gasoline minus the effect of any solvents added for miscability. On other words fairly thick."

Tell me how this isn't the beginning of the disagreement.
 
maraakate said:
As much as I believe that Bwalker is probably right on this as you just gotta be a 2T nut to really grasp or care about any of this... I went back to late 90s and mid 2010s for this article and it's just what he's showing except different layouts at times over the years. The full study appears to have never been published on maximausa.com.
Click to expand...
2-cycles' are fun to work with and repair.

I kept my neighbor's 2-cycle mower going for 20 years when he had his 2-cycle mower. I was amazed at how his mower kept up with my 170cc 4-stroke mower.

I bought a 2-cycle 50cc Honda scooter for the kids when in high school so they could get to their summer jobs; they loved it.

I have had 5, 2-cycle chain saws over the years. I have had a number of 2-cycle trimmers. I had a number of 2-cycle tillers.

In my opinion for the power-to-weight ratio, they are hard to beat.:cool:
 
Here is a study on PIB's in 2-cycle oils which changed formulations:

https://global.yamaha-motor.com/design_technology/technical_review/pdf/browse/35tr0008.pdf

The point of the article was that you can still use PIB's, due to their many advantages, but the PIB's used must be of a lower Molecular Weight and that the introduction of esters in low levels is advantageous.

This shows that even 2-cycle oils must be a carefully Balanced formulation.
 
Last edited:
Bwalker said:
What you are saying is Mr. Molakule is indeed wrong based on your second paragraph.
In first paragraph what you described is what happens prior to the engine coming up to operating temperature.
Click to expand...
No, what I am actually saying is that all your postings have not convinced me of what happens when the fuel/oil mix enters the crankcase of a two cycle engine, and it appears I’m not the only one.
 
Don't know if this contributes to the conversation but once had a Mercury 175 two-stroke outboard that slung a rod through the crankcase. Mercury sent me a new powerhead. My mechanic said he drilled out the carburetor jets to make sure plenty of fuel was hitting the pistons to keep it from getting too hot.
 
Bwalker said:
Cujet, I remember you from DRN years ago. You were into mid bore Husky's if I remember right.
Oils that work well in bikes often dont work so good in things like trimmers and blowers. They can work well in chainsaws. All air cooled power equipment is low BMEP and low load. The exception might be chainsaws when used for things like milling. For trimmers and blowers and oil like Red Armor or Maxima Super M work exceedingly well. In a chainsaw I like Maxima K2. The main thing is to not run a product with castor in it or a heavy weight synthetic like Motul 800 or Klotz R50. Power equipment just does not get hot enough to combust these properly.
BTW one old school syn blend and bright stock based oil that still works acceptable is Golden Spectro. Its not the cleanest, but it works acceptably. Many other better products nowadays.
Click to expand...
Too funny!! I miss that place, lots of good folks. You remember correctly, I had a street legal Husky 360 two stroke. In the end that was a very good bike after critical mods and upgrades were done. Although parts became rather difficult to source. I'd ride it on the fast FL backroads and highway regularly :ROFLMAO: ,and come home with knobby tires worn to the nubs! (worked at the airport and often commuted in and between airports)

I sold the Husky and picked up a KTM 380EXC with a tag. Fun bike, but fell short of the Husky in many ways. Never could get it to run cleanly or be sharply tuned, despite a bunch of effort. It would blubber and ping incessantly. I ended up using pretty exotic race fuels as that actually helped.

The discussion above about fuel/oil separating in the crankcase was likely a factor on this bike. Inconsistent operation was the clue here.

1sGnfqi.jpg
Husky 360.webp
 
MolaKule said:
If you are referring to small 2-cycle engines, the oil/fuel mixture lubricates the bottom end. The oil provides both the lubricating film and the additive mix contained in the oil.
Click to expand...
If you believe in the mist theory which has been proven wrong.
 
The thing I'm not getting is how the description of a "mist" entering the crankcase is opposed - to what either party is presenting.

The definition of a mist is "Fine drops of a liquid, such as water, perfume, or medication, sprayed into the air".
A mist is not a fully evaporated liquid.

The patent used as an example states "According to the aforementioned tests, upon striking the inlet valve and other surfaces of the engine, the oil droplets in the fuel-oil-air mixture coalesce forming visible droplets which then flow along the crankcase surfaces"

Basically the oil separates from the fuel at the intake valve, and other surfaces, right?

The fuel mixture does not remain as a mist after that to lubricate the upper cylinder, is what the patent is referring to as the "mist theory."

Has molakule stated that the fuel mixture remains in a "mist" after entering the crankcase. I don't believe I've seen that.

It basically states that the mixture is indeed a mist when it leaves the venturi.

This does not address the contention that no evaporation takes place before the crankcase.
Is the inlet valve considered to be part of the crankcase?

Does all the theory presented here, address the original disagreement about what the viscosity of the oil is when it arrives in the crankcase?
 
Oil enters bottom end as a mist with carbs. with pre mix. Injected oil gets mixed by air flow and bottom end parts rotation. That's why bearings are caged needle bearings so oil can enter them easily.
My 2 stroke experience is with larger snowmobile engines. 250cc and up, air or liquid cooled. There is always some oil left in the bottom of the crankcase from some separation of the mix BTW.
Lots of turbulence with fuel mix getting pulled into bottom end from piston vacuum, and being pushed up through the transfer ports into the cylinder during the cylinder ''charging'' phase. That air flow is a big part of bottom end cooling and keeping oil in suspension.
There are no intake valves in a 2 cycle engine. Pistons time the cylinder transfer ports which are the intakes and the exhaust ports, controlling intake and exhaust timing by covering and uncovering them. Some engines use reed valves in the intake to boost bottom end air pressure for better cylinder charging and intake tract rotary air valves have been used by Rotax to do the same.
Crankcase is sealed, any evaporation of the mist is trapped in the crankcase and goes into the cylinder and burnt.
2 stroke oil has come a long way increasing engine longevity, even though you can run regular pre mix non detergent 30w oil like Saab did in their 2 stroke cars back in '60's, they will run on it but durability comes into play.
Biggest concern is oil getting into the bearings and on rings. You would have to do an analysis of mixed oil that remains in the bottom of the crankcase to even get a partial read on it. Probably that's how blenders measure their products.
Oil viscosity in a 2 stroke over plain bearing 4 stroke engines are 2 different animals with fuel dilution the big factor.
Snowmobile approved oils are thinner for low temp. flow vs non snowmobile approved and that's the only viscosity references I know of. I've never seen specific grading numbers just temp. usage.
I run full synth. snowmobile oil in all my OPE year round, have for decades with no issues. Klotz is my favorite.
 
repairman54 said:
Oil enters bottom end as a mist with carbs. with pre mix. Injected oil gets mixed by air flow and bottom end parts rotation. That's why bearings are caged needle bearings so oil can enter them easily.
My 2 stroke experience is with larger snowmobile engines. 250cc and up, air or liquid cooled. There is always some oil left in the bottom of the crankcase from some separation of the mix BTW.
Lots of turbulence with fuel mix getting pulled into bottom end from piston vacuum, and being pushed up through the transfer ports into the cylinder during the cylinder ''charging'' phase. That air flow is a big part of bottom end cooling and keeping oil in suspension.
There are no intake valves in a 2 cycle engine. Pistons time the cylinder transfer ports which are the intakes and the exhaust ports, controlling intake and exhaust timing by covering and uncovering them. Some engines use reed valves in the intake to boost bottom end air pressure for better cylinder charging and intake tract rotary air valves have been used by Rotax to do the same.
Crankcase is sealed, any evaporation of the mist is trapped in the crankcase and goes into the cylinder and burnt.
2 stroke oil has come a long way increasing engine longevity, even though you can run regular pre mix non detergent 30w oil like Saab did in their 2 stroke cars back in '60's, they will run on it but durability comes into play.
Biggest concern is oil getting into the bearings and on rings. You would have to do an analysis of mixed oil that remains in the bottom of the crankcase to even get a partial read on it. Probably that's how blenders measure their products.
Oil viscosity in a 2 stroke over plain bearing 4 stroke engines are 2 different animals with fuel dilution the big factor.
Snowmobile approved oils are thinner for low temp. flow vs non snowmobile approved and that's the only viscosity references I know of. I've never seen specific grading numbers just temp. usage.
I run full synth. snowmobile oil in all my OPE year round, have for decades with no issues. Klotz is my favorite.
Click to expand...
The information posted is from a patent that was held up here as proof.
I believe the "inlet valve" that the patent is referring to is indeed the reed valve that some 2 cycles have.
Would you consider a reed valve as a part of the crankcase?
 
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