The SPL is a total synthetic formula, very much unlike the other synthetics out there. Although it will not produce carbon, you may see an increase in carbon residue on your plane because this lubricant has the unique property of breaking up built up deposits and cleaning out the combustion chamber, ring lands and piston top.
Also remember that you will always have some residue since gasoline does not burn clean.
As Brian (flyinwalenda) points out, always use the mixture ratio that the engine manufacturer recommends.
I hope this helps