AFM Ring Failure (Redux)

[Grumpy Bear]

This constant debate over AFM is wearing a bit thin. How many threads are there that deal with this topic? Who knows? Right? 2014 and newer girls. 

 

The GM Service Bulletin No. 10058791-5041 says it’s a ring wear issue of the four deactivated cylinders. Mechanics on this forum are saying it is regarding rings sticking in their lands covered it what they term ‘Coke’. Both are blaming the AFM unit.

 

So let’s do something silly and imagine we’re are level headed and open minded.

 

First question. What do both issues have in common? Loss of oil ring seal that leads to abnormal oil consumption. Is that too far a stretch? Can we agree on that much? Lord!

 

Second question. Do they have anything else in common? Yes both are LUBRICATION issues NOT systems issues. Rings that are under normal loads don’t wear out prematurely when they are adequately lubricated. Rings that have the proper conditions that lead to adequate lubrication don’t Coke up or GUM up.

 

Third question. Do rings on a deactivated cylinder have more load than one that is in operation or less? LESS.

 

Fourth question. Do rings on a deactivated cylinder see more heat or less heat? LESS.

 

That means, if your still in agreement, that conditions that would lead to coking or gumming, if not present during normal operation, are certainly absent during periods of deactivation.

 

Anyone ever caramelize sugar? What does it take to caramelize sugar? What conditions? Three things. 1.) The point at which sugar will caramelize is a property of the sugar itself. 2.) The amount of sensible HEAT. Temperature. 3.) TIME.

 

Same things hold true for fats and oils. Anyone that has ever spent any serious amount of time in a kitchen knows that different oils and/or fats have different ‘smoke’ points. Different ‘fire points’. Different points at which they will ‘scorch’ or turn brown/black and eventually thicken.

 

Motor oil is no exception. Base stocks and additive packages of various groups and additive chemistries also have different smoke points, fire points, Noack values and thermal oxidation rates and incipient levels based on….drum roll please….TIME AND TEMPERAUTURE.

 

Time in a motor we count in miles or hours of operation. Temperature is specific to the exact point in the motor the oil is subject to but most will concede that bulk oil temperature on the pan is indicative of?????  Thermal oxidation points and rates. These tables have been published for decades and get updated from time to time based on the current best chemistries and operating conditions.

 

The hotter you run it the shorter the time it takes to degrade it to the point of failure. The weaker the chemistry the quicker and lower those two points have become. Castor bean oils I’ve seen fail in hot running, freshly built (tight) Brit single motorcycle motors in under 50 miles. Turn to asphalt.

 

Lubrication failure is the ROOT CAUSE of an AFM ring related failure regardless the end result being wear or gumming. That’s what you want to debate? Not relevant.

 

Motors running too hot with oil of inadequate chemistry for too long a period of time. It is that simple. It’s got zip to do with complexity of design or the function of that design.

 

Since there is no way GM can detect what oil was used for the length of time it took to cause the failure this TSB is there best spin on saving face for a public that is adamant on its own destruction. 

 

Y’all want to run the lowest chemistry available in a motor that under design conditions is running WAY to hot but insisting that you run it multiples harder and hotter for a length of time you deem commensurate with good cost effectiveness. Garbage oil, run too hot for extended intervals and then cry like babies blaming GM and the AFM system. Even decent oil under those conditions is a crap shoot.

 

Now, you can disagree. Think I’m a nut job. Hiss like a box of snakes if you like. I really don’t care. Do what you want and I’ll do what I want. Think what you like. I’ll believe the science and not the myths.

 

Today’s oils might not be your fathers oil but neither is the motor you’re putting it in. Every time the chemist makes an improvement in oi the manufacture uses 105% of it pushing government regulation, consumer cry and….good old fashion GREED.

 

Flame away boys. I’m not listening…….I won’t be revisiting this thread so have a nice day.