change the oil thats whats MOST important...get those early wear/metals
outta the engine...
then consider what youre trying to really achieve w/ synthetic vs dino...
if youre gonna continue to change your oil & filters at 5k intervals then
the ADDED cost of the synthetic isnt worth it (in my mind).
to justify the 3x cost of synthetic, for me, i EXPECT to get at least 3x
the mileage from it (and im not willing to run my oil 15k w/out a change
of the filter & oil....truth of the matter is id personally want 20-25k miles
per oil/filter change if i were gonna go the the expense of synthetic.
remember one of the IMPORTANT benefits of an oil & filter change is
that youre REMOVING impurities (metals, coolant, fuel etc) when you
drain that oil & change the filter thats trapped the garbage.
if youre gonna go sythetic then i HIGHLY recommend that you periodically
SAMPLE the oil to determine whats in the oil and if the oil is falling out of
spec <lower flash point, viscosity reduction, etc>
im not a huge fan of the synthetics...but i DO run 'em where fluid isnt
often changed (rear ends & trannies) and in all my motorcycles (which
dont see a LOT of uses....these days)