It could be a coincidence. Which oil is it? Several years ago, when synthetics came out first of all, there were issues with seals and the oil, but then the manufacturers realised that's no good for them and worked on the formula so that decent oil helps prevent the seals from leaking.
Cheers
Tim
They didn't go all at once -)
The oil was Fuchs 5W40 Easter based, which I agree is very very good oil!