synthetic oil

why does synthetic oil not burn as much in a ringed out old smoker voyager van vs regular everyday oil?

I believe that would be due to the viscosity changes with temperature being slightly different with the synthetic. That is: the oil might have the same viscosity 'cold' such as at room temperature, versus 'hot'. But that in-between those extremes, or at the peak temperatures (pistons & piston rings are always hotter than the motor oil) the synthetic oil acts like its a little thicker. I dont know that this is entirely good - thicker oil isnt the answer to ALL lubrication problems.
And it could be a lot of your oil burning is due to valve stem seals that are senile, and letting oil run down the intake or exhaust valve guides.

I would think you are using as much or more synthetic, BUT synthetic oil does not really burn at all because it is synthetic. It is not real oil, it is a man made substance. If you look at the smokeless 2 stroke oil they sell for small engines you will see it is synthetic. It is lubricating but not burning during combustion.