What protects when the oil's cold?

[Curious Kid]

As the cold season is upon those of us in the northern hemisphere, cold start protection seems to become one of those naging concerns. Beyond cold starts though, I'm curious to know what it is that protects the components from wear while the engine (and other devices I suppose, like the transmission and diff.), as I have heard that much of the additives in past oils required heat to do there thing? - I'm thinking that the activation heat in friction zones would have to be from higher friction (increased wear), to overcome the decreased fluid and component temperature to start with.

Aside from the increased viscosity creating a theoretically tougher film, this may leave small voids and clearences starved of oil - the wiped and fuel washed piston ring zones are one area that quickly comes to mind. There's moly and esters I suppose, but can anyone be more clear and spacific about this?

What are some of the ideal temperature zones for commonly and perhaps not so commonly used additives? I thought I recall a reading where ZDDP didn't really start to exhibit much in the way of wear protection until it (the oil), was at or above 70 deg.c.

Thanks in advance.

 

[626LX2.0LATX1998]

just use synthetic 5w30. you should be good. no worries.

 

[LarryL]

Let the people that formulate your oil worry about all those details. 626 et all, has it right, use a synthetic 5w30 and be happy.

 

[Curious Kid]

I hear you guys.

I was wonder more on the lines of the workings of the lubricant and additives, that's all. Wanting to learn more, you know. For something so seemingly simply and often used without conscious thought, I find all the properties and conditions facinating. I guess I'm strange like that on many levels, though I figure I'm just researching the things that interest me to know more about what it is I'm really dealing with - curbing disillusionment.

Again, if anyone would like to share further insight, thanks in advance for posting. We could all benefit I feel from obtaining a deeper understanding. Am I mistaken thinking that this is one of the key points of this board?

Kid.

 

[JAG]

I'm with you Curious Kid. Some people want to know exactly how things work, others don't. Your questions are very valid, and fortunately, Molakule has already made some posts answering these questions. Not sure what forum they are in, but with some searching you should be able to find them. I do recall him saying oil makers put in several anti-wear additives that work in different temperature ranges to provide as much protection as possible from cold to operating temps.

 

[labman]

Anybody ever hear of a pseudo plastic index? Pseudo plastic refers to the decrease of viscosity as shear goes up. Thus, when the engine stopped, the oil would thicken up and stay put on the bearing journals and camshaft lobes. On a cold start, it would thin out and become pumpable.

 

[MGBV8]

Engines fitted with low temp thermostats (or worse no thermostat) can have a lot more wear (3times) in the front cylinders than the rear cyls, possibly because the cool coolent from the the radiator hits the front cylinder or cyls first and then heats up as it moves back.

 

[bruce381]

"Anybody ever hear of a pseudo plastic index? Pseudo plastic refers to the decrease of viscosity as shear goes up. Thus, when the engine stopped, the oil would thicken up and stay put on the bearing journals and camshaft lobes. On a cold start, it would thin out and become pumpable."


No never have but in the industry we do know SSI or shear stability index which is a measure of viscosity LOSS from the viscosity GAIN do to whatever VII is being tested.

Straight grade oils are shear stabile and show no shearing loss what you are discribing is a "thixatrope" ?spelling?
which will thicken upon setting and thins when subject to shear but then thikens back up again upon setting, that is a common thing with grease but not so with PCMO's.

Even VII improved PCMO,s show none of this tendecy if they shear they stay that way.
bruce

 

[Curious Kid]

Interesting.