I rebuilt the OMP 5K miles ago.
I know it pumps as I broke the one line when I rebuilt the engine and mistakenly repaired it the first time with rubber tubing which resulted in oil over the right side of the engine and exhaust manifold. (Mini panic when smoke started rolling out from under the hood. Since repaired with silicon tubing.)

But with 165k miles I've gone to also premixing at 1/2 oz of 2-cycle TC-W3 to 1 gal gas.

Are there any disadvantages, performance or otherwise, to premix + OMP?

 

Too much oil can foul the spark plugs.

 

Don't think I'm there yet.
Short drive this morning, enough to get to operating temp and then some.

Pulled a leading plug and it was grayish-tan in color, which is normal.

Thanks for the warning.

 

too much oil causes the engine to run lean.

THink of your carb as delivering x amount of liquid for y amount of air. Y doesn't change but the x is divided between oil and gasoline. If there is more oil than gasoline in the mixture the amount of x being delivered that is burnable is less. So you deliver more air than fuel to burn. Lean.

 

I premix 2oz/gallon and run heat range 10 spark plugs and I don't have fouling issues.

I'd premix more but the exhaust starts to get visible on cold start/driving.

 

Not true. It might be true IF you were adding significant amounts of oil - I mean way more than the ~60:1 that I run, which is only altering the amount of gasoline by less than 2%, not enough to worry about - but oil also burns, so it is a fuel, so it doesn't really affect fuel mixture to begin with.

Racing Beat advocated running premix in the range of 4-5oz/gallon on 600hp turbo engines. This is still only about 4% oil/96% gasoline...

 

Just relaying advice I got from an old two stroke flat tracker racer.

 

Two-strokes use an order of magnitude more oil than rotaries would need. At that point, you might not only see effects of different BTU/volume in the oil versus gasoline, but viscosity changes altering carb jetting could also come into play.

We're not running 10-15% oil, though

 

I have a stock 12a with an unmodified Niki on top.
I went with low-ash 2-cycle oil as it is intended to mixed and burn.
My 1:256 ratio is just for a little insurance. I'll check the plugs every Fall in preparation for winter hibernation.

Getting my igniters finally sorted out cleared up many long standing performance issues. Intermittent is far worse than totally dead in terms of problem solving.

 

At that, you really shouldn't see too much of an issue. Plugs can be changed every two years anyways and I check mine every 6 months. Just had them out and cleaned them in my 80 yesterday. I just like to know how the engines are running and if any adjustments should be made to the carb. So far so good and this is a principle that I've used for the last 18 years.