[V8] synthetic back to dino oil

[Tdehoff at aol.com]

Group I have read that going from Conventional to Synthetic oil in a High 
Mileage car can cause lots of trouble with leaking.  This is my question, I have 
a 1990 V8 with 145K on it.  The prior owner said he used only synthetic oil in 
it.  Would I be okay to switch back to conventional oil?  I change my 
vehicles oil every 3 months regardless of mileage in all my other vehicles and I 
usually have some where between 2000 to 5000 miles on them at the time. 

Tom 
90 V8 145K