Depends on how long you plan on keeping it.
If going to sell/trade it in a few years...go with the OEM recommendation
If going to keep it a looooong time, then what I do is change it at 500
miles not matter what. Ditto tranny, ditto Diff
Yes, old timer stuff and still believe in it...even with the new IP
in them these days
I do switch over to synthetics at that time and add my molyB additive
in all, except an automatic tranny or diff with clutches
For used, I do that first chance and usually within the first days
or week of ownership
