Quote Originally Posted by Tri-Z Pilot
Yes I agree, but let's say you have stock jetting, and you have no reason to change it, by mixing more oil in with your gas you are making it leaner, that is if you dont compensate the jetting for a mixture change. Your cooling system whether it be air or liquid, really has noting to do with cooling you piston, it's the incoming fuel charge. As for the lubrication, I can see the more oil you put in would cause stress more than friction. You would be stressin the crank/rod and bearings, but friction would go down because of more lubrication between the piston and cylinder, but as you said why use more than you need, so it is best to meet in the middle somewhere.
Simply put, if you add more oil to your gas, it does not change the fuel/air ratio, and does not make it leaner or richer. It does slow the burn rate of the fuel resulting in what looks like a richer condition.

The hotter a motor runs, the faster it burns fuel, and the leaner it will look. Your fuel charge insignifanctly cools your piston. Your piston will reach the ambiant temperature of the inside of the burn chamber within a few degrees. You can affect the piston's temperature by three things. 1. You can control the temperature of the fire. Leaner, which means less fuel and more air makes a hotter fire, (like blowing in a campfire). Adding oil to gas, slows burn rate, and reduces the temp of the fire. 2. You can control the temp of the chamber walls with cooling fins or water jackets, which results in reducing the temp of everything going on inside that chamber. If you dont believe liquid cooling affects piston temperature, I posted a picture of a piston that melted as a result of an impeller failure a while back. This is why bike run so much "richer" until they reach operating temp. 3. The final factor is friction. This is what makes the quality of your cylinder wall lubricant is so important, as well as making sure you are getting enough of it. Less friction=less heat.