In the late 1950s, I bought a used mid-1950s Allstate Cruisaire (see photo). Ten years later, I acquired a used 1963 Allstate. Back then, I use just plain SAE 30 oil for the 2% pre-mix according to the operator's manual. While it worked, I had real problems with the plug fouling and killing the engine. When that happened, the usual next step was to coast off to the side of the road, take off the engine cowl and remove the spark plug with the Piaggio included spark plug wrench. A small carbon deposit could be seen between the electrode and ground. The carbon particle was removed using a finger nail and off I went again. It was a real pain. Fast forward to the present time, I rebuilt the 1963 Allstate to 150 cc. I also acquired a 2005 US PX150. In both cases, I started to use the Motul 710 100% synthetic 2T oil for pre-mix in the Allstate and for the auto-lub in the PX150. Since then, I have never experienced a plug fouling as a result of a carbon deposit. The new fully-synthetic 2T oils are so much better. I feel they are worth the price. A quart at Amazon cost just $17.45 and will last for a long time. It is worth the peace of mind knowing I will not encounter an engine-killing, plug fouling, carbon deposit while riding. I also feel they provide better lubrication over a wide temperature range.
One more thing, if you use auto-lube and ride in colder weather, the fully synthetic 2T oils will maintain their viscosity for easy flow and not thicken as do the non-synthetic oils. This is a minor issue but something to think about.
Here is the Amazon address for the Motul 710 2t 100% synthetic oil. Shipping is free.
https://www.amazon.com/Motul-104034-710-Synthetic-Motor/dp/B00C739LTY/ref=sr_1_2?keywords=motul+710&qid=1565578530&s=gateway&sr=8-2