Two thoughts:
1> Synthetics, both Group IV based as well as Group III based, contain esters in the blend. The original intent of the ester content was to promote controlled elastomeric seal swelling to counter the shrinkage when traditional PAOs were used as motor oil that resulted in synthetics' notorious leakage problem. (Solvent refined Group I based motor oil lube stocks have cyclical ring "aromatics" left over from the original crude oil. These aromatics have a solvent quality that promote seal swelling. Unfortunately, aromatics are not good lubes. However, in addition to their seal-swelling qualities, esters are superb lubricants in their own right because they're also polar molecules which aid cleaning and adhere by charge attraction to the molecule-thick oxide coating present on all metal surfaces - unforeseen functional bonuses...)
But, before you race to dump in a full changeout of Mobil 1 in your tidiness-challenged engine...
2> Since synthetics are "slipperier" than their Group I solvent refined counterparts, normally a sterling quality, that extra lubricity can often allow leakage past seal flaws which would otherwise be impenetrable, or nearly so, to conventional motor oils.
If you're confused by these contradictory synthetic qualities, it's evident you're thinking. (always dangerous...) I'd venture if your engine is already leaking with conventional oil, it'll be at least as bad (and likely even worse) with synthetic motor oil until you track down and repair the leak(s).