Well - it's pretty cheap to OCI a Dmax.
But at some point, we toss aside the worry of the money on a UOA, because we're after the facts and data, right? I often am amused at guys that are willing to OCI with synthetics at OEM intervals, and act as if money is no object, but then they scoff at UOAs that show them they can go MUCH further. (I'm not picking on you personally; it's an observation of some habits some folks get into). As you know from over at DP, some folks will dump syns at 5-7k miles because it's "cheap insurance", but then ignore the UOA data they pay for ... Go figure .... I mean you no personal offense; I'm poking at the masses here.
Why not use the Fumoto, get the UOA, and see how accurate the OLM really is? Take a "live" sample with the engine warmed up and running; it's easy with the Fumoto. You won't loose enough volume that a top off would be necessary. Here's how I do it:
1) with a cold engine, clean off road dirt from valve
2) start engine and drive around until warm
3) park and leave running
4) grab tools and bottle
5) one last cursory wipe of valve
6) use pliers to remove spring (if you have one) and then open valve for collection
7) close valve
