You know i've heard that before about using synthetics in older engines proning them to more frequent leaks,i know from using nothing but Mobil one in my truck since just about new '01 model,i don't see any leaks...
One of the problems when Synthetics were first introduced for auto engines is that the oil would cause some of the old elastomers, like Buno, to swell and soften from a chemical reaction. I don't think that's been a problem for the last 25 yrs or so especially since oring and elastomer gasket material for sure has caught with these oils. I've been running synthetics in all my daily drivers since the early 80's with no problems.
