There are claims that switching to synthetic on an old motor can cause leaks to
appear...apparently synthetic oil does not cause rubber seals to swell as much as
conventional oil, so as the seals shrink leaks are possible.   However, I've never
experienced this problem...switched to synthetic in my '85 vanagon in '93 at 65K miles.
Mark

James Shinosky wrote:

>         Mobil One oil sounds very appealling to me... I m considering change over to
> Mobil one in my three autos. But my Vanagon has around 15K on its rebuilt
> engine and the two autos has 72K and 116K on them. Is it too late to change to
> Mobil One?
>
> James
> W88kender
> Anaheim, Calif.