Risk of losing prime of the scavenger pump during oil change

[Dalamar]

When doing an oil change I've always just changed what's in the main oil tank and haven't drained the sump also (or what I can from the sump). I've always worried about losing the prime on the oil pump as even with just the tank oil change I sometimes get a momentary 0 psi oil pressure warning on first start. Also, previous owners had receipts that showed dealers only doing the oil tank change and charging for 5-6 L.

So, is there anything to worry about if I drain the sump oil too? I know there's meant to be still plenty of oil left in the sump for the scavenger pump to get hold of but what are people's real-world experiences? I would be a real pain if the pump lost its prime.

Is it best and safer to just change the oil in the tank more often than 12 months?

[Modrich]

I drained the sump and then disconnected the fuel pump so I could turn it over without it firing-up and top-up the oil level, i do it to half way when cold.

[Basil Brush]

If you give it time when refilling then some of the new oil will drain back into the sump.

As above, you can pull the fuel pump relay and turn it over to prime.

[Dalamar]

Thanks Modrich and Basil.

That gives me confidence to drain the sump oil next time around. I prefer to measure the oil when cold too and the halfway mark is about the same for my car.