Originally Posted By: OVERKILL
Keep in mind though that HTO-06 isn't the only high heat deposit control test.
Yes, sure. I just used HTO-06 as an example of a certification that pays attention on high heat deposits. Of course, there are many other parameters.
Originally Posted By: OVERKILL
This is one of the reasons I have a very hard time accepting varnish as "harmless". Because if you see it, then it is elsewhere in the engine, and if it is in the piston/ring-land area, it has the potential to affect compression, oil drain-back and generally lead to poorer performance and possibly consumption.
I've never considered varnish as harmless. The simplest explanation is that varnish prevents proper cooling of pistons and rings. Consider it as a blanket: usually heat exchange chain is "piston->rings->cylinder wall->coolant". If rings are covered by varnish, less heat comes out, higher piston and rings temperature, more varnish and deposits sits on piston and rings and another loop started.
Originally Posted By: OVERKILL
The thing is, my friend who had the mess of an engine didn't run synthetic in it, only conventional. But I don't think that was the problem.
IMO, this is always a compromise. Using some synthetic oils tends to heat deposits, conventional oils leaves varnish. Also not any car can work with dyno.
When I many years ago came here I was surprised that nobody flush engine during oil change. This is a common practice in Russia even now, and
a number of flush service oils is available. This cleans varnish from the engine and removes the rest of dirty oil. Because of no such oils are available here, I would recommend to use
LIQUI MOLY Pro Line Engine Flush. Please, no Gunk Flush
It is just a solvent, but German product has over 4000 ppm of moly.
Originally Posted By: OVERKILL
I've never torn down, or been involved in the tear-down/witnessed the tear-down of an engine that was clean and also had stuck rings or plugged oil return holes. But all the ones that HAVE had that problem had one thing in common: varnish.
I had exactly this situation on my Maxima 2005 (traded-in now). Engine was perfectly clean, but oil consumption was more than a liter per 1000 miles. Changing PCV did not help, compression was 245 psi (!!). Pure oil compression. Of course, catalytic got spoiled too. And this happen on 108k miles only.
So what is a resume of my long talk? Keeping engine healthy is not as simple as 1-2-3, especially if the car has direct injection and/or turbo. The approach "I bought a barrel of oil on a sale because it was dirty cheap"
could work, but this is not my way. And if we keep in mind that neither manufacture nor dealer needs you car lasts longer, this becomes not a trivial task. Much more complex than "read your manual and use what is written there".