How did you determine that the proper OCI for all-4 of your vehicle engines are 6k OCIs?
Are the oil brands and grades all the same too?
That's Interesting!
I maintain four vehicles and I adopted three different OCI timetables - three different oils - two different filters - two different grades of oils. I adopted a mind-frame on what's best for the engines and not what's best for things like simplifying the routine. I use a phone calendar and notification system for reminders, since mine appear different and a little more complicated from yours. In the old days, I hung a wall calendar on the garage wall for scheduling maintenance matters.
Whatever works best for each individual and each individual vehicle I guess. That's all that matters-most.... trying to make both the maintainer and the engine happy campers.
I vote for the Supertech filter every 6k OCI btw.