The SAE paper (2007-01-4133) specifically notes that there is a vis increase, and that increase is non-detrimental at the valve train. However, it also acknowledges the concerns of fuel economy from parasitic drag in the cylinder, where surface area affected by vis is much greater than at the valve train.
In short, it's a balancing act.
The thing I'm trying to get across to people is that shorter OCIs generally are a total waste of money. You don't "gain" any wear reduction; you actually increase wear in shorter OCIs. While it may be counter-intuitive to the layman, it makes sense when you see the studies and data.
There are certainly times when shorter OCIs are warranted; heavy contamination or sludge. But those are not nearly as common as some believe, and I have always excluded such examples from my generalizations. I would NEVER suggest extending an OCI when there is a known problem that cannot be mitigated without phsical intervention, or stalling with OCI frequency. And that is really what it's all about; you have to KNOW your equipment, and your lubes, to really understand what is good/bad decision wise. Too many people here blindly take a "kitchen sink" approach; they throw everything at the lube interval (short OCIs, syns) and call it "good" and they have no idea how define acceptable condemnation limits, and are unaware of how far out even conventional lubes can successfully go.
As I've said (and it's in my signature line) ...
ANY lube can be over or under utilized.
In short, it's a balancing act.
The thing I'm trying to get across to people is that shorter OCIs generally are a total waste of money. You don't "gain" any wear reduction; you actually increase wear in shorter OCIs. While it may be counter-intuitive to the layman, it makes sense when you see the studies and data.
There are certainly times when shorter OCIs are warranted; heavy contamination or sludge. But those are not nearly as common as some believe, and I have always excluded such examples from my generalizations. I would NEVER suggest extending an OCI when there is a known problem that cannot be mitigated without phsical intervention, or stalling with OCI frequency. And that is really what it's all about; you have to KNOW your equipment, and your lubes, to really understand what is good/bad decision wise. Too many people here blindly take a "kitchen sink" approach; they throw everything at the lube interval (short OCIs, syns) and call it "good" and they have no idea how define acceptable condemnation limits, and are unaware of how far out even conventional lubes can successfully go.
As I've said (and it's in my signature line) ...
ANY lube can be over or under utilized.
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