One can google on the prudence of switching high mileage
vehicles to synthetic. A lot comes up. It seems there are a
tiny number of such vehicles that experience leaks after
such a switch. Most seem to do fine or even better on the
synthetic, though.

"FunkyKev" <lee.kevin@comcast.net> wrote
> 1998 Accord V6. 190k. Always used Castrol 5-30 regular
> or high
> mileage. No leaks, no smoke, no nuthin'...ever. Any
> reason to switch
> to Full Synthetic at any point...especially now? Thanks.