Opti-2 at 92:1?

[Cujet]

Can someone explain the chemistry/physical attributes that allows these 100:1 oils to perform like a 50:1 oil? Do additives make up for less liquid portion?

Sure, I'd be happy to describe exactly how the wear rate changes with oil ratio. For most 2 stroke engines from OPE to outboards, the more oil one uses, the lower the wear rate. But to be clear, 32 to 1 provides about as much protection as 16 to 1. 50 to 1 increases wear rate slightly, and anything over 50 to 1, regardless of oil brand or choice, increases 'under load' wear rate markedly. Especially on the exhaust port side of the piston rings.

The idea that higher viscosity or higher concentrations of additives make up lack of oil is simply not true. 50HP 125cc Kart engines use 24 to 1 or more.

 

[ripcord]

Sure, I'd be happy to describe exactly how the wear rate changes with oil ratio. For most 2 stroke engines from OPE to outboards, the more oil one uses, the lower the wear rate. But to be clear, 32 to 1 provides about as much protection as 16 to 1. 50 to 1 increases wear rate slightly, and anything over 50 to 1, regardless of oil brand or choice, increases 'under load' wear rate markedly. Especially on the exhaust port side of the piston rings.

The idea that higher viscosity or higher concentrations of additives make up lack of oil is simply not true. 50HP 125cc Kart engines use 24 to 1 or more.

So my saws that ran for 1000's of hours on 72:1 Opti-2 mix would have lasted longer on 50:1 Stihl,Echo,Generic mix? I'm not claiming technical expertise here, but that wasn't my experience.

 

[Cujet]

So my saws that ran for 1000's of hours on 72:1 Opti-2 mix would have lasted longer on 50:1 Stihl,Echo,Generic mix? I'm not claiming technical expertise here, but that wasn't my experience.

125cc liquid cooled motocross bikes were for a time, using TCW3 with great results despite its supposedly lower quality. And plenty of people use 50 to 1 or less and never wear out their engines. But when it comes to objective testing, more oil is generally better. Wear rates decrease as oil nears 32 to 1.

Of course, there are other aspects. More oil reduces octane, and even a tiny amount of knock can increase damage and wear. However, when engines are properly manufactured, assembled and tuned, run on adequate octane and so on, repeatable results exist.

Please note, I don't predict disaster with a lean oil ratio. Disaster really only happens when we totally forget to add oil.

 

[The_Eric]

I haven't use the Opti-2 oil but I looked the other day (before I wrote my initial post, on the prev. page) at the oil's SDS and it shows:
Kinematic Viscosity: 13.4 cSt @ 100ºC; 101 cSt @ 40ºC

Page 5, Section 9, 2nd column, 2nd to last line
The PDF is from May 2025.
https://opti2-4.com/wp-content/uploads/2025/10/Opti-2-Two-Cycle-SDS-5-2025.pdf

Those are properties of a 40 grade oil, so I guess it's rather thicker than thinner oil. That's why it can be run at 72:1 similar to Amsoil Saber which people run 80:1 and 100:1. Other 2-stroke oils for both OPE and motorcycles are much thinner that that, with properties of a 30 and 20 grade oil. The last may cause major failure if run lower than 50:1 ratio. I know people who run ATF which is about 5 cSt @ 100ºC (very thin oil) but they run it at about 20:1 (25:1) ratio.

The most important when run 2-stroke oil is to know what upper rod bearing the engine uses - needle rod bearing or just a bushing bearing. Most of todays engines run needle bearings and are fine at 50:1 ratio or lower with thicker oil. However, older engines with bushing rod bearing should not be run on leaner than 25:1 ratios, regardless of the oil thickness.

After looking at the KV40 viscosity, there's no way what I have matches what is claimed.

 

[Japanese]

After looking at the KV40 viscosity, there's no way what I have matches what is claimed.

Can you post, please, a picture of the front and back label of that Opti-2 oil?

 

[The_Eric]

Can you post, please, a picture of the front and back label of that Opti-2 oil?

 

[Japanese]

After looking at the KV40 viscosity, there's no way what I have matches what is claimed.

The PDF above should be acurate because this is the Opti website and the same PDF is there as well:
https://opti2-4.com/safety-data-sheets/

 

[ripcord]

It looks like they haven't updated their package branding in 25 years.

 

[lilspenny]

Just some general opinions. I've been running Stihl equipment at my workplace without issues for over 4 decades by just following the owner's manual recommendations. I was taught that 2 cycle engines are designed to operate best at wide open throttle under load. Too much idling is not good. Running at half-throttle, load or no load is not the best.

Another concept many don't understand is that running significantly more oil in your mix actually means that the engine is running leaner on gasoline (more oil = less gasoline). Think about it. This may require carburetor tweaking to compensate, which many don't have the technical knowledge to comprehend/perform. And, increasingly many 2 cycle engines no longer have easy accessible carb adjustments. Why not just follow the owner's manual?

I wonder if people are having engine issues because they simply don't follow the general principles above? I.E., piddling around the yard with the string trimmer at half-throttle with the incorrect fuel mix much of the time.

I believe that wot may help in some cases but I don't believe wide open throttle for long periods of time is good, as that may lead to insufficient lubrication and engine damage. There needs to be a balance between rpm, heat, and fuel/oil/air ratios that will protect the engine. A lot of uninterrupted time at wot may mandate more oil. Running the same ratio under all conditions sounds nice but when the heat goes up so does the risk of seizure.

 

[doitmyself]

I believe that wot may help in some cases but I don't believe wide open throttle for long periods of time is good, as that may lead to insufficient lubrication and engine damage. There needs to be a balance between rpm, heat, and fuel/oil/air ratios that will protect the engine. A lot of uninterrupted time at wot may mandate more oil. Running the same ratio under all conditions sounds nice but when the heat goes up so does the risk of seizure.

I agree with the first part of your first sentence, but not "uninterrupted time at wot". People don't tend to operate their outdoor power equipment for 5, 10, or more minutes at WOT the entire time. You go about your work a minute, two, or three and release the throttle to move to the next action, section, whatever. Excessive idling is not good. Doing your work (cutting, whipping, blowing) at half throttle is not good either (my main point).

For fun, I Google AI'ed the statement "2 cycle engine runs best at wide open throttle" and the answers are pretty good. We're not allowed to use AI here. I still stand by my opinion. And of course, on an Alababa 95 degree day you want to operate with the heat in mind.

 

[ripcord]

The worry about leaner mixtures with more oil is a little over blown, IMO. A 50:1 is 2% oil and a 32:1 mix is 3.125% oil or 98 and 96.75 percent fuel, respectively. The difference between the two is quite small in terms of a stoichiometric ratio.

 

[Japanese]

The worry about leaner mixtures with more oil is a little over blown, IMO. A 50:1 is 2% oil and a 32:1 mix is 3.125% oil or 98 and 96.75 percent fuel, respectively. The difference between the two is quite small in terms of a stoichiometric ratio.

Exactly. I'm trying to explain that to some people on here.
As we saw from posts above the optimum lubrication for 2-stroke engines is 32:1. And actually lean on oil is much more dangerous than lean mixture because of more oil which is insignificant. The facts show that people always blow their engines because of insufficient oil, not because of too much oil.

I've ridden my 2-stroke vintage bike with 25:1 and richer on oil and never had a failure for years. He needs it because it has a bushing wrist pin bearing vs needle bearings. So how lean is that mixture and why I've never blew the engine?

 

[97prizm]

Hey guys, I've decided to go the polar opposite in 2 stroke oil.. I'm a bit tired of smelling the smoke as I'm out there doing weed eating the ditches and other parts of the yards that I maintain.. Isn't Opti marketed as a 100:1 oil? Their 1.8 oz pouches mix at 71:1 in a gallon though? I buy alkylate fuel in a 1.3 gallon jug, so that would put me at 92.2:1 so I'm a bit torn. Should I mix at 71 or 92:1? I'm leaning towards 92:1...

I realize there are many who advocate mixes at 50, 40 and 32:1 and I'm usually one, I just want to try something different and if stuff blows up then ooops! I guess that would mean that I would have to upgrade.

I run my Stihl at 40:1 like they say. It's not smokey or smelly. I want it to last, messing with ratios could be an issue. I just saw this 2 stroke oil on Lowe's website. It says something about It's an (EDG ++) rated oil. We
Hen I looked that up it said that was slightly tougher specs than JASO FD. Never seen it on the shelf however.