Motor Oil 101

Status
Not open for further replies.
Originally Posted By: Dominic
naa actually its a GM engine, the popular 3800-II, and is spec'd to run that high. Thanks though
smile.gif



Coming to this discussion 12 years late, where does one find such a spec? I've never seen a spec (in either ideal viscosity meaured in mm^2/s) nor lbs/1krpm for any vehicle. I dont doubt such exist, but i have never seen them shared with the public.

How did you find yours?

G
 
Quote: "3 - Racing viscosity
It is well known that the heavier viscosity oils such as10w-60 Helix Ultra are more tolerant of fuel dilution than the lighter 5w-40 versions. They usually have a much higher HTHS viscosity too"

I track and occasionally race a street-legal, but fairly dedicated track car. After ~ 10 track days and a couple thousand miles i change my oil and typically do a UOA. My dilution is "unmeasurable". I conclude that the extended high heat of track use boils off undesirable elements, and suggests that raced or track-used cars may be able to accept longer change intervals, not shorter. I also measure no significant shear down, and minimal additive diminution as measured by % phosphorus and zinc which are more of less still at label strength.

Counter to "common wisdom, yes, but the facts.

-G
 
quote: "From the above a 0W M1 does not appear to provide sufficient protection in high temperature scenario and a 15W50 is used although with an ester based oil a 5W or 10w can be used."

I see that it's HTHS is lower. I do not see any evidence based threshold, so i see nothing to tell me whether it "does not provide sufficient protection .....". I will also note that the official definition of HTHS is resistance to viscosity breakdown, and the definition of viscosity is resistance to pumping. All this leaves me woozy as to whether it is a good measure of high temp, high speed, protection of sliding (including rotating bearing) surfaces under pressure.

It DOES seem that a flow rate is proportional to oil (in bearing) replenishment rate, and it also seems that these fluids are in compressible. So a refreshed fluid - meaning high flow would be best, Viscosity reduces flow. Ergo my uncertainty, and Dr. Haas' assertion.

What concerns me is why the established advice is so clearly counter to this. Someone is clearly not understanding something - likely subtle. And maybe the somebody is me.

G
 
Last edited:
I think I'd benefit from your version of the same topic, step by step.

Along the way either support or slay sacred bovines, please :)
 
Originally Posted By: just_me
I will also note that the official definition of HTHS is resistance to viscosity breakdown, and the definition of viscosity is resistance to pumping. All this leaves me woozy as to whether it is a good measure of high temp, high speed, protection of sliding (including rotating bearing) surfaces under pressure.


Where did you get these definitions ?
 
Originally Posted By: Merkava_4
Originally Posted By: SilverFusion2010
Thread necromancy


I had to look that word up. Never heard of it.
grin.gif



more like necrophilia
 
The HTHS def was from the abstract/summary of the ASTM method (i don't have login priv for the full method, which i wanted). Viscosity was from deep memory in physics, and from some recent documents i perused trying to unravel seemingly conflicting positions - i don't recall where.

Good to see replies on such an old thread. Any clarification welcome. The more step by step (and detailed) the better.

G
 
Last edited:
I went back and did more reading (not on oil related sites!) on viscosity. Not having truly studied fluid dynamics, the **implications** (which is what we care about) of what I'm reading is still elusive. I now have several definitions that I'll simplify and consolidate into "an arbitrary unit, applied to the fluid, measuring the force required to maintain a constant differential speed between two surfaces separated by that fluid". Since a force applied to the fluid would have to overcome that same force relative to the container wall surfaces (pipe, bearing..) it *will* in fact be opposition to pumping as well, but that's a corollary, not the basic property.

So, none of this jumps out and says "more is better to protect the parts". In fact, intuitively, it seems that with sufficient viscosity a) huge force will be required to keep those surfaces moving (heat, friction) b) huge force will be required to pump in new fluid as old is expelled, meaning potential for decreasing volume and failure.

for the record, that force is F=uA (v/A) where F= force, u= dynamic viscosity, v=relative velocity and A = shared area of surfaces. I use V rather than u since I cant type "mu" :)

Obviously, companies with high research budgets have studied this. I'd like to know what they in fact found. Step by step.

G
 
Originally Posted By: just_me
So, none of this jumps out and says "more is better to protect the parts". In fact, intuitively, it seems that with sufficient viscosity a) huge force will be required to keep those surfaces moving (heat, friction) b) huge force will be required to pump in new fluid as old is expelled, meaning potential for decreasing volume and failure.


OK, next you have to go and research "hydrodynamic lubrication"...viscosity is only one item in the equation of keeping parts separated.

Per the underlined bit you have fallen into the "flow equals lubrication" camp, which is plain incorrect. Pumping oil into stuff doesn't "lubricate it" (unless it's a hydrostatic bearing or a turbine on barring)

BTW, what is the definition of "huge", and what is "normal"...
 
I do find it interesting that Redline's 5W40 has such a margin in HTHS vs similar grades from M1 and Castrol/Edge. yes I checked:) I note that the same cannot be said for other "premium"brands including most of the German ones or Amsoil. If HTHS is as useful as normally presumed, their 5w40 should offer the best of both.

G
 
I'm well aware of the various states of lubrication. Walk me through the fluid dynamics of why flow isn't lucubration; it certainly not the whole story, but i'm looking for analysis, not dogma - ergo the open ended questions asking if any are able to go through the theory step by step. I'm not...but more than willing to listen and learn.
 
Status
Not open for further replies.
Back
Top