New LSPI article.

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Thanks for sharing. Excellent read and fascinating. Still leads towards Sodium and Calcium as being the main culprits along with their ability to "hold" fuel in the oil during cold engine usage (dilution).


From the link shared by the OP
“It has nothing to do with the amount of oil in the combustion chamber, or if the engine is consuming oil or not. There’s going to be oil in the upper ring zone in every properly lubricated engine. It’s a question of whether the oil in the upper ring zone has a tendency to hold fuel, or not. If the fuel mixes with the oil, and the oil creates an emulsion, if you will, where it holds the fuel in the oil, that’s where things can begin to go bad,” says Speed.

It’s perhaps this one single quote that really tells the tale of their entire testing session. Based on the information shared with them from the ORNL testing, and backed up by the discoveries they made during the EFIU test sessions, all indications point to particular detergents acting as the root of the problem.

Where we talk above about sodium being highly reactive is where they received their first clues.

“In the end, you end up with this third chemical which is neither fuel nor oil, and the octane value of this third chemical is lower than the fuel or the oil, so it is what detonates,” says Speed.

“And that’s the challenge, because when it detonates, it all burns off and then it’s gone. For example, we could run the engine in a certain way to kind of load up the ring zone with this fuel/oil/soup combination, and then make a power run. In that first power run, you’d see several knock events, especially higher magnitude knock events. Then you could instantly make a second run, and the number and magnitude of knock events would diminish. By the third run, they are all gone. The engine was consuming and burning off all of the soup of unburnt fuel and oxidized oil that was reacting together because of the detergent holding the fuel in suspension.”
 
My brother still runs the cheapest gasoline he can find in his 2017 Chevy Malibu and 2017 Chevy Cruze both with a turbo-charged direct injection engine.

I think he gets the first couple of oil changes free from the dealer. I told him that he has to use the right kind of oil in them to prevent low speed pre-ignition, and that he should run high test gasoline in them. He does do his own oil changes, so it will be interesting to see if he uses the proper oil, and also if using cheap gas will cause those engines to self destruct.
 
I could well be wrong but I have heard that some people have found running higher octane actually helped prevent LSPI from happening?? I could well be wrong but that rings a bell to me.
 
Hmm....not so sure about this 'third chemical' malarky. This being the third chemical that inconveniently disappears the moment you start looking for it! Sounds to me too much like The Grassy Knoll conspiracy theory!

I'm no expert but I might also take issue with the assertion that there will ALWAYS be an accumulation of oil in the space above the top ring. There will be a thin residual film of oil on the bore on which the top ring slides but certainly on the power stoke, the primary action of the splayed ring will be one of downward scraping and not allowing oil to push upwards through the first groove (the gap is effectively sealed by the mating up of the top ring upper face and the top edge of the first groove). Movement of oil through the 'open' top ring gap will be countered by the rapid downward flow of blow-by gas through the gap.

Will unburnt/partially burnt fuel accumulate in the space above the top ring? IMO, in a TGDI/GDI engine, yes; especially at low temperatures or at start-up or when you have a gasoline with a particularly heavy back-end. Might this fuel accumulation leech oil from the thin film of oil on the surface of the bore? IMO, yes. Might it also act as a 'puller-upper' of oil from under the top-ring? IMO, possibly yes. Might tiny quantities of oil which exit the crackcase with blow-by gas, traverses the PCV/Intake system to be burnt also accumulate in the fuel collected above top ring? IMO, yes. Might this mix of unburnt/partially burnt fuel and oil have a really low octane rating? Deffo. Might the occasional 'throw-off' of this accumulated gunk into the combustion chamber cause an LSPI event? Yes. Might particles of Calcium, Magnesium & Sodium have differing catalytic properties once they're in play in the combustion zone? Yes, I could imagine that too.

However all this stuff about calcium, magnesium and sodium being mega-reactive is hokum. These metals do not exist in oil in their pure metallic state; they exist as the carbonate salt which is thermally very stable and only ever does something in the presence of an acid. And this stuff about calcium detergent 'holding the fuel in suspension'; that's just bollocks! Fuel and oil and oil additives are all readily solvable in one another. Likewise the liquid fuel won't actually 'see' Magnesium or Calcium in a detergent. All the fuel will see is a load of long alkyl chains that cover the tiny, colloidal suspended metallic carbonate particles.

Oh, and why are these guys testing what look like 40-weight HDDO's to investigate a phenomenon that only happens in gasoline engines? That does not compute!
 
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"Oh, and why are these guys testing what look like 40-weight HDDO's to investigate a phenomenon that only happens in gasoline engines? That does not compute!"



Yep. One would think they would test with 0/5w-20 and 5w-30.
 
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