What oil is best? and what ratio?

[Da dog man]

Any word on motorex cross power 2T?

 

[PissRev]

Any word on motorex cross power 2T?

It's an excellent oil and is the oil that comes in every KTM, Husqvarna, and GasGas 2-stroke bikes.

 

[Da dog man]

Got a buddy w two ktm's that swears by it he gave me a partial bottle to try in the saws so we shall see

 

[redneckhillbilly]

what do you think the octane rating of 91 non ethanol gasoline is, after its mixed 40:1 with 2 stroke oil?

 

[farminkarman]

what do you think the octane rating of 91 non ethanol gasoline is, after its mixed 40:1 with 2 stroke oil?

It has been a minute since I have looked at a report on this topic. I will see if I can find it again. I want to say that that 50:1 was estimated to drop effective octane rating between 1 & 2 points depending on the oil used.

 

[PissRev]

what do you think the octane rating of 91 non ethanol gasoline is, after its mixed 40:1 with 2 stroke oil?

I asked Mr Google that question just exactly like you posed it here and this was the response from AI:

When you mix 91 octane non-ethanol gasoline with 2-stroke oil at a 40:1 ratio, the resulting mixture's octane rating will remain essentially around 91 octane because 2-stroke oil does not significantly affect the octane rating of the fuel; it's primarily designed for lubrication, not combustion properties. [1, 2, 3]
Key points to consider: [1, 2]

• Negligible impact on octane: The small amount of oil added at a 40:1 ratio is too insignificant to noticeably change the fuel's octane level.
• Focus on lubrication: The primary function of 2-stroke oil is to provide lubrication within the engine, not to alter the fuel's combustion characteristics. [1, 2]


Generative AI is experimental.

[1] https://shopmotul.com/2-stroke-oil-explained-everything-you-need-to-know/
[2] https://canberradiamondblade.com.au/how-to-mix-2-stroke-fuel/
[3] https://www.eia.gov/energyexplained/gasoline/octane-in
-depth.php

 

[redneckhillbilly]

huh interesting, I would have guessed it would have cut it down 10 or so points.

 

[PissRev]

huh interesting, I would have guessed it would have cut it down 10 or so points.

Yeah man who knows if this is actually correct but this is what Google Gemini AI came up with.

 

[bwalker]

do you guys think enviromental factors come into play, like humidity, temperature, mixed with altitude air density. would that have an impact on oil performance in different regions-climates?

I've been running 40:1 dominator since I started reading this thread a few years ago, I can notice an increase in power over my old mix of husky oil at 50:1, but its got me wondering if maybe the fuels and climates favor that mixture for me here, and someone in a different region might need a completley different recipe.

No.

 

[bwalker]

Is that how ester do?? Dom leave a oil film that is not as greasy as Saber on the bottom end, Super M and K2 both do leave a film like 90 weight oil with a hair of tacky feeling. Man I should stop buying different oil and stick to one lol.
Those 4 oil I've tried are all good. Maybe just some different characteristic.
Almost forgot to mention the bean oil Maxima 927, that stuff is gummy! Not really mean for chainsaw I think.

I have never noticed any oil to be "sticky". Some pre mix oils are thicker some are thinner.

 

[bwalker]

what do you think the octane rating of 91 non ethanol gasoline is, after its mixed 40:1 with 2 stroke oil?

What's it matter? Saws have such low compression ratios it's pointless to worry about octane.
Also consider that the fuel air mixture inside the combustion chamber doesn't have a significant amount of oil in it. The only time it does is prior to the engine coming up to temp, which is one reason two strokes smoke more at startup.

 

[farminkarman]

What's it matter? Saws have such low compression ratios it's pointless to worry about octane.
Also consider that the fuel air mixture inside the combustion chamber doesn't have a significant amount of oil in it. The only time it does is prior to the engine coming up to temp, which is one reason two strokes smoke more at startup.

I beg to differ...I used to think I could get away with efree 87 for my ported saws. I have had a couple that wouldn't shut off....I have only had it happen once since I switched over to 91 efree, and in that case, it was an issue of too much timing advance. Some saws even after machine work will never get enough compression to have issues, but some can up there in a hurry.

 

[bwalker]

I beg to differ...I used to think I could get away with efree 87 for my ported saws. I have had a couple that wouldn't shut off....I have only had it happen once since I switched over to 91 efree, and in that case, it was an issue of too much timing advance. Some saws even after machine work will never get enough compression to have issues, but some can up there in a hurry.

You are describing pre ignition, which octane doesn't prevent. As you mentioned your timing was too far advanced.
I run premium E Free or Canned fuel because it's gives you a cushion for volatility loss induced octane degradation and is insurance if you have a high load lean excursion.

 

[bwalker]

Some oils do indeed lower octane slightly while some actually raise it. If the oil uses a stoddard solvent or kerosene diluent octane will be degraded. However some oils use high octane diluents that actually raise octane. One example is Honda HP2 which uses cumene Cumene has an octane of 108.

 

[lehman live edge slab]

Lots of guys including tree monkey say detonation in a saw is really hard to do even at over 200 lbs compression. But i haven’t tested it so i wouldn’t know from experience, was a few guys building pretty high compression saws like 220 and still running 87 but I don’t know if they had issues.

 

[bwalker]

Lots of guys including tree monkey say detonation in a saw is really hard to do even at over 200 lbs compression. But i haven’t tested it so i wouldn’t know from experience, was a few guys building pretty high compression saws like 220 and still running 87 but I don’t know if they had issues.

Tree monkey is a smart guy and is right.

 

[ammoaddict]

Lots of guys including tree monkey say detonation in a saw is really hard to do even at over 200 lbs compression. But i haven’t tested it so i wouldn’t know from experience, was a few guys building pretty high compression saws like 220 and still running 87 but I don’t know if they had issues.

I put an 028 super piston in a Husqvarna 55 once, it had 250 lbs compression, no detonation. I could have been running 90 octane, can't remember. It ran really good but was a nondecomp cylinder and too hard on starters so I took it back out.

 

[Mastermind]

I have a Poulan 3750 with 230psi. Never had detonation, but it is impossible to keep tuned.

 

[jakethesnake]

Hate a saw that needs to be tuned every time you run it. Had a couple. They sit on shelves now

 

[Mastermind]

Hate a saw that needs to be tuned every time you run it. Had a couple. They sit on shelves now

I need to pull it apart and dish the piston.