Originally Posted By: Shannow
So when you leave the oil in place until you start to get that uptick in "wear" per 1,000 miles, where exactly on the cost-benefit curve are you ?
$20 of oil, versus $8k of engine ?
My bro's fire protection company where maintenance downtime is more vehicles, registration and insurance costs, plus lost opportunity has a FAR different break even (think losing the vehicles before factory warranty has expired, and choosing the manufacturer with the longest warrantable service interval), versus Saturday arvo and a jug of oil bought on clearance.
First of all, do NOT presume that an uptick in wear is automatically implying emminent destruction of the equipment. If one is operating at 2ppm of Fe per 1k miles, and it goes up to 2.3ppm or even 3ppm per thousand, that is NOT an indication of impending doom. It's just a place marker to start paying more attention, UOAs perhaps sooner, and looking for the approach of commendation levels (such as 150ppm total Fe, etc). Just because wear goes up after being incredibly low, does NOT mean harm is happening to an engine, tranny, gearbox, bearing, etc.
The cost/benefit sir, is to manage the overall maintenance program to a point that gives the highest ROI, WITHOUT causing undue harm to the equipment.
Let me flip this onto you. Where do you believe the prudent delineation lays? All you seem to do is want to look at inputs. If the vis is "X" and the FP "Y" and the soot is "Z", then OCI? Heck, if low input numbers is the goal, then why not OCI every week? Why not OCI every 500 miles?
What if the vis was fine, but the wear rate had up-ticked to 3x it's "normal" rate. I mean, if you are willing to ignore the wear rates whey they are low, then by extension you should be wiling to ignore wear rates whey they are high. If Vis was spot on in the middle, and FP was good, and soot was low, by your logic the oil is OK to continue? But what if those were true AND the Fe was 200ppm, the Cu was 87ppm, and so on. What if the Fe wear rate was 4ppm/1k miles, rather than a nice low 1ppm/1k miles? You see, your logic, when turned against itself, fails. (edit - Shannow, I am not stating this is your mantra. What I'm doing is playing devil's advodcate here.) If we accept that you don't want to use wear metals to acknowlege a healhty engine, then you cannot really use them to infer an engine in detrimental state. So if wear metals were high or wear rates escalated, then as long as the lube properties were OK, you'd be alright with continuing the OCI? Get the point I am making here? In your plan (or at least how I think you are objecting to my paradigm), you want to focus on vis, FP, acid/base, soot/ox, etc. I want to focus on metals. I am not willing to ignore the inputs, but in my program they are used as trigger points to further scrutinize the wear. Conversely, you would focus on inputs and let wear run amok? You cannot have your cake and eat it too! I will not accept an argument that says "Well, we cannot trust low wear rates; we must focus on the vis and acid. But if metals are high, then something is wrong ..." That is a duplicitous argument. You either believe that UOAs give insight to wear, or you don't. If you ONLY believe that lube properties are the key to good maintenance, then what would be your explanation for a failing engine that was showing heavy wear? Say for example, you OCI every 5k miles, and the Pb and Cu are atrocious (indicating heavy bearing wear), but by gosh, the vis and FP and ox are all good, so just keep on doing the OCIs until the main bearings screech to a halt? If you are like me, then you have faith that wear metals cannot only tell you when something is wrong, but when something is right. While I agree UOAs are not a panacea of info, they are the low-cost reasonable view that is the quickest and easiest tool we have to establish wear. So my question is this:
If your lube properties were OK but your wear metals were horrible, would you just continue the OCI because the lube is fine?
The point of lubricant is to reduce wear. I do understand it is also to clean and to cool, but those are in effect sub-inputs to the reduction of wear. If the engine were dirty, but still wearing well, what does it matter? If the engine were silly-stupid hot, but wearing nicely, what would it matter? THE NUMBER ONE REASON TO USE LUBE IS TO REDUCE WEAR. THAT IS THE OUTPUT TO CARE ABOUT. ALL OTHER THINGS ARE INPUTS. All those things you purport are important in that they are reasons to pay closer attention to wear rates, because they may alter the wear rate sooner rather than later. But if the wear rates are low, and the contamination is low, then why plunder into an OCI? What manner of thought gives logical conclusion to change a product that is well in control?
I am not immune to the concept of risk. For several years I helped manage a maintenance program at a Ford facility in Indy. We used UOAs, but also used IR (infra-red heat identification) and RFI (resonant frequency isolation aka vibration analysis). I (and others) had oversight to the HVAC equipment, waste water facility, powerhouse steam generation and huge air compressors. We were in charge of many tens of millions of dollars of equipment. We understood the risk of being penny-wise and pound-foolish. In fact, we had several DD engines for our stationary fire pumps; those are HIGHLY CRITICAL items to manage. Here are the condemnation levels I used:
Fe overall of 150ppm, or Fe escallation of 3ppm/100 hours as a rate slope
Cu at 100ppm, or escalation of 2ppm/100 hours as a rate slope
Pb at 50ppm, or escalation of 2ppm/100 hours as a rate slope
etc ...
If vis got above 20% of the starting VOA, then it was time to UOA more often. It was NOT time to OCI, because those giant engines had large sumps. It was cheaper to UOA. So if vis got thicker, or FP dropped, or acid/base flipped, I would UOA more often to watch for a wear increase above my allowable slope. Our standard sample was 100 hours, but if conditions changed, we'd UOA more often, watching to see if the escalation of the attribute was going too fast for the next OCI cycle.
Fact is, in small engines (cars, personal trucks, motorcycles, lawn mowers, etc) it's not cost effective to UOA frequently, if at all. It's just cheaper to OCI.
But if you DO UOAs, and the UOAs tell you that wear is under control and below both a magnitude total AND a wear rate curve, then why OCI? It's a waste to pay for information and then ignore it!
I ask you, that if you don't subscribe to my mantra of a planned, well-managed, well-rounded maintenance plan based upon OUTPUTS, then what are the criteria YOU would change oil for, and why? Prove to me that vis "X" is safe but others are not. Prove to me that acid/base is detrimental at ratio "Y". You see, if you condemn a fluid based on an arbitrary vis or FP, it's not any different than condemning a fluid at an arbitrary OCI distance (miles or hours).
There is a class you should go take if you get the chance; it's called "Shainin" Red X. It is a root-cause analysis discipline. The thrust being this: if you change an input and the output does not change, then the input does not matter at that stage. Only if you can manipulate the input, and turn the output on/off repeatedly via the input, can you claim causation. Without correlation, causation is impossible to exist. You cannot avoid this fact of life.
So in regard to inputs (vis, FP, acid/base, etc), please show me that your methodology has merit. Show me that changing oil at duration ("Q") is beneficial if you cannot affect wear at that point.
That is the challenge I put to you.
