I bought my ser with 200k, when I switched to mobile1, I got 50 leaks all over the motor. I was leaking from my oil pan, oil pump, all upper seals, cam seals, dizzy...ect.
Nothing crazy but it was there almost within a week (my DD). I was leaking about 1 quart a month.
I eventually retired the motor after changing the crank seal on both sides and still having too many leaks.
What happens is the better additives in the oil help to break down the crud that has worked it's way into small cracks or gaps in your seals. Then, once the cracks are cleared, you get oil seepage....
I have mobile 1 in my ve from dre, not one leak yet...1 year and counting DD'd.
Down here at school there are allot of master mechanics that work in our motorsports department, they swear by Amsoil and say mobile 1 isn't terrible but isn't the best out there for the price......your pick.
Lastly, one of the largest benefits about synthetic is it resists changes in viscosity due to cold weather. Helps out with cold starts, no matter the climate.
Dudeman