I don’t think there’s a right or wrong answer for all engine types. There are a lot of variables involved across engine families. And wear-related variables within an engine family. And driving patterns.

It is true that modern (heck, even old dino-juice) oil will persist on surfaces for months, years, decades (I also disassemble (Porsche) engines that have sat for months, years, and decades.)

It is also true that the persistent oil film will protect surfaces during startup.

What is also true is that that oil film will “go away” very, very quickly once the engine fires and is idling at ~800 RPM (~13 revolutions per second.) In that context, the difference between ~0.2 seconds and ~0.8 seconds for full oil pressure is accelerated main and rod bearing wear. Ring wear “doesn’t care” about this: Piston rings are not pressure fed oil. Hydraulic lifters are pressure fed; they care about time-to-pressure.

One thing that varies considerably across engine families is the length and topology of the oil path from oil pickup, through the pump, and to the main and rod bearings and lifters. In the flat-4/6 engines that path is short and mostly horizontal. In a deep sump V8 that path is long and can be mostly “vertical.”

Long story short:

- I have observations for many, many Porsche V8s. There is an observable difference on the time to register full oil pressure that is proportional (but not linear) to how long they’ve sat and that, in the context of decades, pre-oiling appears to have a positive impact on crank and rod bearing wear.

- For the flat-4/6 engines they can - it seems - sit for at least a year with no observable difference in the time to register full oil pressure.

So, for the Porsche V8s, if they’ve sat for ~4+ months (over-winter) I think “pre-oiling” is a good idea. For the flat-4/6s, I am not worried about it provided that they are run once per year. Last, even if it was the case that I was worried about it on shorter timescales, the problems don’t begin to manifest for decades. So, a once-per-year dry start won’t manifest problems for ~20 years and if in between dry starts you’re driving 7500 miles in 20 years you have… how many miles on that engine? Enough that putting new bearings in it might be a good idea no matter what. And if you are driving 100 miles between yearly dry starts then it’s a collector car / objet d’art and bearing wear doesn’t matter.

 

Clear Flood will get oil pressure to the timing chain tensioner, valve lifters, and variable valve timing mechanism before the engine starts firing. You can hear the clatter after an oil and filter change.