Originally Posted by OVERKILL
Varnish is the precursor to sludge. It is a sticky layer of precipitate that indicates that the contaminant carrying capacity of the lubricant was exceeded. It is generally deposited on cooler areas and/or areas of low oil flow, which is why the cylinder head surface is a common location to observe it. This also means that it has a propensity to build up in low-flow areas like ring lands where the lubricant is not in forced motion. Accumulation in this area results in oil control problems, which then present as consumption and can ultimately result in ring sticking, blow-by and loss of compression if it gets bad enough.
While engine designs are generally tolerant of a bit of varnish and thus typically asymptomatic, this should not cause one to thus conclude that varnish is harmless. Like many human maladies, the causes of which are well-known, an underlying condition that hasn't manifested into something impactful is still a condition nonetheless.
As I'm sure many recall, BMW reduced their OCI length due to issues they were experiencing, so I'd be wary of using that marque as an endorsement. As engines become more complex, various systems will, as Trav demonstrated, be less tolerant of this type of accumulation. Low-tension rings will be more inclined to stick for example, leading to consumption.
I'm not endorsing it by no means, I'm saying a little varnish is nothing to worry about in most cases where poor engine design isn't going to create a problem as a result. I'll take the literally thousands of engines I've seen with varnish operating just fine other than valve cover leaks or a faulty rocker or whatever was the issue that had us looking into the engine over some forum internet worry. Sorry. Not gonna change my mind on it.
Varnish is the precursor to sludge. It is a sticky layer of precipitate that indicates that the contaminant carrying capacity of the lubricant was exceeded. It is generally deposited on cooler areas and/or areas of low oil flow, which is why the cylinder head surface is a common location to observe it. This also means that it has a propensity to build up in low-flow areas like ring lands where the lubricant is not in forced motion. Accumulation in this area results in oil control problems, which then present as consumption and can ultimately result in ring sticking, blow-by and loss of compression if it gets bad enough.
While engine designs are generally tolerant of a bit of varnish and thus typically asymptomatic, this should not cause one to thus conclude that varnish is harmless. Like many human maladies, the causes of which are well-known, an underlying condition that hasn't manifested into something impactful is still a condition nonetheless.
As I'm sure many recall, BMW reduced their OCI length due to issues they were experiencing, so I'd be wary of using that marque as an endorsement. As engines become more complex, various systems will, as Trav demonstrated, be less tolerant of this type of accumulation. Low-tension rings will be more inclined to stick for example, leading to consumption.
I'm not endorsing it by no means, I'm saying a little varnish is nothing to worry about in most cases where poor engine design isn't going to create a problem as a result. I'll take the literally thousands of engines I've seen with varnish operating just fine other than valve cover leaks or a faulty rocker or whatever was the issue that had us looking into the engine over some forum internet worry. Sorry. Not gonna change my mind on it.
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