I have a '95 Merc 200HP EFI. The oil pump was removed and I premix 50:1. I use Penzoil XLF.
I use my flow meter to determine how much fuel I burned on the last trip and then I add enough oil to fill up again before I leave the house. On the way to the ramp I stop and add the requisite gas.
I marked an old oil jug in gallons of gas at 50:1 to simplify the oil calculation.
