Reasons for scoring of cylinders and failure

[Sapientoni]

I notice there are engine failures where the cylinders are scored and the reason(s) are listed as unknown. My personal suspicion is incorrect oil viscosity, not in compliance with mfgr. requirements. People have a tendency to be opinionated, myself included, and if you believe strongly for whatever reasons, that this oil or that oil is better for a given application, there may be unexpected consequences. The reason for cylinder scoring is "underlubrication or failed lubrication". There could be failure of the plating on the pistons that causes some problems, but it's certain the engine has "cylinder lubrication jets" in the crankcase. It's certain these jets are sized for a specific viscosity of oil. Changing this viscosity, changes the amount of oil passing to the cylinders and also the distance the oil is injected up the cylinders. Think about it!

[Scnell Gelb]

Yes there are oil squirters. Perhaps they get plugged? Or as you suggest do not pass sufficient oil in low temps.
The conventional wisdom on the Forums seems to be that the oil for cold climates should be 0w-30w or thereabouts. Many people seem to use 15-50 year round -even in cold weather.
A quote from THE authority on this subject who kindly shared his experience:
"The factory did not allow for adequate running clearance in cold temperatures with these engines, especially those that have forged pistons. After being just started the piston expands faster than the cylinder and the clearance becomes too tight, which makes it impossible to gain boundary layer lubrication from the engine oil. To make it worse, the oil is still cold and thick when this occurs as its only seconds after cold start up.

Cayenne engines have the same issue and its so bad that a couple of Canadian dealerships send us their engines rather than installing a crate engine that will just do the same thing all over again. One Cayenne owner has had this occur 4 times!

We have done much more of our testing in super cold, than in super hot. Next month we'll have a test car start a 20,000 mile loop of N America. I wish he was on the road now, taking advantage of all these awesome opportunities to see single digits and below zero values. Then we'll take it apart and see how it looks. The record on one of our test engines is 5,200 cold start cycles.

If you have to drive in the cold try to keep the car stored in a warm environment and when driving down stay parked so long that the engine completely cools down!
__________________
Jake Raby"

[Sapientoni]

When I saw the 2006 Lincoln zephyr called for 0w-20wt I could not believe it.

[BYprodriver]

Originally Posted by Sapientoni

When I saw the 2006 Lincoln zephyr called for 0w-20wt I could not believe it.

Yeah same here. The Porsche oil squirter's hit the underside of the pistons to cool them

[Sapientoni]

Even with a rod bearing gone plus .006" into the crankshaft journal (didn't measure the rod damages) there was no trash in the crankcase squirters of the 2006 3.4 I rebuilt. I had some superficial scuffing n replaced 2 pistons but my scuffing was from bearing fragments being pushed off.

[Jeff Alton]

What do the "experts" describe as "cold weather"? And is the 0/40 or 5/40 vs 0/30 really the cause?

[Scnell Gelb]

The quote in #2 above answers one of your questions.
There is no clearance for any lubrication.
"...the piston expands faster than the cylinder and the clearance becomes too tight, which makes it impossible to gain boundary layer lubrication..."
Which is why the advice is - 'don't start the engine in very cold weather'.
In marginally cold situations, lighter oil may make just enough difference to avoid scoring but I have read no precise definitions of the parameters.

[Jeff Alton]

Sorry, was the recommendation to use 0/30 in the yet to be defined cold temps? If so are you saying a 0/30 performs differently in cold temps than 0/40? Is this scoring still evident in warmer climates?