dnewton3
Staff member
I’ve often been very vocal in professing that synthetic fluids and bypass filtration are tools for making the fluids last longer in service, and not the equipment. I’ve been challenged in a couple PM’s to show the rationale, so here goes.
Consider the available resources we have today that we commonly use and hear about on BITOG. UOA’s (and to a lesser degree, Particle Counts) give us very good data to use. But we have to know how to interpret the data, and where to apply the resultant decisions. UOA’s show us a spectral analysis of particles in the 1-5um range. They don’t tell us the size, but they tell us the composition and frequency of occurrence (ppm). With that in mind, we make assumptions of how well our equipment is enduring, based upon what type and quantity of metals are shed. For any given criteria, we have the fortune of lots of data accumulated here on BITOG, and through services such as Oil Analyzers and Blackstone, to name a few. From that, we acknowledge that certain accumulations are “normal”; i.e. – we place a numeric value as an upper limit. For example, we might say Cu should be no more than 8ppm, or Fe should be no more than 12ppm, and so on, for a “typical” exposure (duration = mileage). Anything above the limit indicates it’s time for an OCI; anything below the line represents continued use. And it’s not just wear metals, but viscosity, TBN, insolubles – we all know the drill, right?
Now, it’s very common to hear claims that synthetic oil, and bypass filtration, will protect equipment “better”. I’ve always been the contrarian that says “better” is a relative term, and that you can simply offset this perceived advantage by changing your conventional oil and filter more often. Therefore, synthetics and/or bypass filtration are tools for making lubricants last longer, not equipment.
In the graphs I’m putting forth, you have to accept that for the sake of clarity and expediency, I’ve made them of simple shapes and sizes. In reality, the ongoing ebb and flow of UOA’s do have the nature of some variability. The lines in the graph represent averages. If you were to take UOAs every 100 miles, you would get more data points, but overall they can be averaged to represent the slope of the lines. Further, I applied a bit of logic in that after you would OCI with fresh oil, there is always some amount of residual oil from the last load, so you never get a true “zero” ppm for any wear metal. In this case, I chose 2ppm of residual. What’s important to understand is that it’s not the values, but rather the area under the curve, that represents wear. I’ve put it in simple terms of “units” of wear. I took the quantity of ppm, and multiplied by the mileage factor (5,10,15, etc) to come up with a total area under the curve. The area under the curve shows us, in effect, the amount of wear that has been experienced as an expression of accumulated wear metals.
When you view the charts, notice that the total average of wear under the curve is identical. The reality is that there would surely be some small differences, but over the long haul, the anomalies would even out, and the total “average wear” unit would equal, or be darn close to it. I also concede that wear will show a small blip after an OCI, as touted by the SAE paper, but that paper is quite old by now and may not be relevant to today’s oils. These graphs take into account results, not inputs. They are indeed hypothetical, but they do represent the conceptual realization that there is some basic growth pattern in wear patterns over the lifecycle of an oil sump event.
When using UOA’s, you have (or should be) committed to using limits as the determining factor to OCI. If 10ppm is your upper limit, you’re not going to OCI until that 10ppm limit is reached. It could be Cu, Fe, Al, or whatever. It could be 10ppm, 12ppm, 7ppm; it doesn’t matter. The important thing to note is that DATA should drive the decision to OCI, and not emotion.
In this first graph, you’ll see that Synthetics and Bypass filtration can give a nice long OCI. That’s because they keep the ppm’s down well in the beginning of the graph. But look at the second half. You spend just as much time above the average as below the average. With that in mind, the total average wear is 180 units for this graph. The math is simple. The 2ppm for the whole 30k miles represents 60 units, and the triangles represent 120 units. The total is 180 units.
g-1
http://www.bobistheoilguy.com/dnewton/PPM_graph_1_1_oci.jpg
Now, look at this next graph. Conventional oil and filters are changed more often. But, again, we drive up to the 10ppm limit, and then OCI. Guess what? The area in the 6 smaller triangles is equivalent to the area in the one large triangle; 120 units. The net average wear is the same at 180 total units!
g-2
http://www.bobistheoilguy.com/dnewton/PPM_graph_2_6_oci.jpg
So, what is the conclusion to take away from this information? Did synthetics and bypass filtration protect better? No; not the way I see it. The average wear is the same. It’s important to note that the graphs are simple geometric shapes, and that reality throws curve balls at us some times. We surely realize that the slopes have some curve to them, but the concept to understand is that they will likely be of similar nature between the two scenarios; only the duration of exposure changes. The net conclusion is thus: synthetics and bypass filtration protect longer, but not better.
“Well, Dave, I’m taking better care of my equipment than you because I use synthetic and/or bypass filtration and I change my oil every 10k miles.” OK, go back and look at the charts. What you’ve done is move the “acceptable upper limit of wear” from 10ppm on the synthetic graph to somewhere down around 5ppm (you created a new limit on the Y-axis). We can accomplish the same thing with the conventional oil by just decreasing the OCI interval so that our limit is 5ppm as well. That might be estimated at 2.5k miles or so (as resultant on the X-axis). People often want to force conventional oil into a mandatory OCI term, but then judge it against a synthetic that is allowed to artificially lower the wear limits. Again, with UOA’s, the correct mentality is to establish acceptable wear limits, and run your oil out to the full term. If you do this, you don’t get less wear with synthetic and/or bypass filtration, you get more life cycle of the fluid. The reason synthetics and bypass filtration can show better numbers at the same OCI is because they are more capable. But it’s an unfair comparison. The goal is to limit wear, not OCI duration. It’s no different than asking one person to run 40 yards and measure them in seconds (time as a variable), but then tell the next person to run for 40 seconds and see how many yards they run (distance as a variable)! You have changed the fixed and variable metrics!
There is a side-line issue of synthetics being more, shall we say, temperature capable. That’s true, but only in a very narrow context. For cold weather, synthetics only offer a significant advantage below -15 deg F or so. But how many of us really operate in such an environment for much duration, if ever? Some do, but they are a very small minority. Further, what about heat protection? Presuming your cooling system is working correctly, conventional oils do just fine. Synthetics would only protect better if an overheated condition were to exist, and only for a limited time. As the temp rises quickly, there is a very small window of opportunity for the synthetic to succeed where the conventional would fail. After that window closes, any oil would fail, regardless of group composition. It is also true that synthetics resist evaporation somewhat better than conventional oils, but does that make the engine better protected? No, it simply means the synthetic oil lasts longer. The make-up oil is a consideration of cost, not wear.
Now, I’m sure that some of you might still be in the “Yeah, but …” camp. Well, I don’t know that I’ll ever be able to convince you otherwise; nor would you be able to convince me. We will have to agree to disagree. But in my mind, given the intent of wear analysis, synthetics and bypass filtration make fluids last longer, not equipment. If you don't run up to your established acceptable limits, you're cheating the fluid, and your wallet. And if you do run up to the acceptable limits, then wear is the same, and the return is in fluid life cycle; equipment life cycle is the same.
Consider the available resources we have today that we commonly use and hear about on BITOG. UOA’s (and to a lesser degree, Particle Counts) give us very good data to use. But we have to know how to interpret the data, and where to apply the resultant decisions. UOA’s show us a spectral analysis of particles in the 1-5um range. They don’t tell us the size, but they tell us the composition and frequency of occurrence (ppm). With that in mind, we make assumptions of how well our equipment is enduring, based upon what type and quantity of metals are shed. For any given criteria, we have the fortune of lots of data accumulated here on BITOG, and through services such as Oil Analyzers and Blackstone, to name a few. From that, we acknowledge that certain accumulations are “normal”; i.e. – we place a numeric value as an upper limit. For example, we might say Cu should be no more than 8ppm, or Fe should be no more than 12ppm, and so on, for a “typical” exposure (duration = mileage). Anything above the limit indicates it’s time for an OCI; anything below the line represents continued use. And it’s not just wear metals, but viscosity, TBN, insolubles – we all know the drill, right?
Now, it’s very common to hear claims that synthetic oil, and bypass filtration, will protect equipment “better”. I’ve always been the contrarian that says “better” is a relative term, and that you can simply offset this perceived advantage by changing your conventional oil and filter more often. Therefore, synthetics and/or bypass filtration are tools for making lubricants last longer, not equipment.
In the graphs I’m putting forth, you have to accept that for the sake of clarity and expediency, I’ve made them of simple shapes and sizes. In reality, the ongoing ebb and flow of UOA’s do have the nature of some variability. The lines in the graph represent averages. If you were to take UOAs every 100 miles, you would get more data points, but overall they can be averaged to represent the slope of the lines. Further, I applied a bit of logic in that after you would OCI with fresh oil, there is always some amount of residual oil from the last load, so you never get a true “zero” ppm for any wear metal. In this case, I chose 2ppm of residual. What’s important to understand is that it’s not the values, but rather the area under the curve, that represents wear. I’ve put it in simple terms of “units” of wear. I took the quantity of ppm, and multiplied by the mileage factor (5,10,15, etc) to come up with a total area under the curve. The area under the curve shows us, in effect, the amount of wear that has been experienced as an expression of accumulated wear metals.
When you view the charts, notice that the total average of wear under the curve is identical. The reality is that there would surely be some small differences, but over the long haul, the anomalies would even out, and the total “average wear” unit would equal, or be darn close to it. I also concede that wear will show a small blip after an OCI, as touted by the SAE paper, but that paper is quite old by now and may not be relevant to today’s oils. These graphs take into account results, not inputs. They are indeed hypothetical, but they do represent the conceptual realization that there is some basic growth pattern in wear patterns over the lifecycle of an oil sump event.
When using UOA’s, you have (or should be) committed to using limits as the determining factor to OCI. If 10ppm is your upper limit, you’re not going to OCI until that 10ppm limit is reached. It could be Cu, Fe, Al, or whatever. It could be 10ppm, 12ppm, 7ppm; it doesn’t matter. The important thing to note is that DATA should drive the decision to OCI, and not emotion.
In this first graph, you’ll see that Synthetics and Bypass filtration can give a nice long OCI. That’s because they keep the ppm’s down well in the beginning of the graph. But look at the second half. You spend just as much time above the average as below the average. With that in mind, the total average wear is 180 units for this graph. The math is simple. The 2ppm for the whole 30k miles represents 60 units, and the triangles represent 120 units. The total is 180 units.
g-1
http://www.bobistheoilguy.com/dnewton/PPM_graph_1_1_oci.jpg
Now, look at this next graph. Conventional oil and filters are changed more often. But, again, we drive up to the 10ppm limit, and then OCI. Guess what? The area in the 6 smaller triangles is equivalent to the area in the one large triangle; 120 units. The net average wear is the same at 180 total units!
g-2
http://www.bobistheoilguy.com/dnewton/PPM_graph_2_6_oci.jpg
So, what is the conclusion to take away from this information? Did synthetics and bypass filtration protect better? No; not the way I see it. The average wear is the same. It’s important to note that the graphs are simple geometric shapes, and that reality throws curve balls at us some times. We surely realize that the slopes have some curve to them, but the concept to understand is that they will likely be of similar nature between the two scenarios; only the duration of exposure changes. The net conclusion is thus: synthetics and bypass filtration protect longer, but not better.
“Well, Dave, I’m taking better care of my equipment than you because I use synthetic and/or bypass filtration and I change my oil every 10k miles.” OK, go back and look at the charts. What you’ve done is move the “acceptable upper limit of wear” from 10ppm on the synthetic graph to somewhere down around 5ppm (you created a new limit on the Y-axis). We can accomplish the same thing with the conventional oil by just decreasing the OCI interval so that our limit is 5ppm as well. That might be estimated at 2.5k miles or so (as resultant on the X-axis). People often want to force conventional oil into a mandatory OCI term, but then judge it against a synthetic that is allowed to artificially lower the wear limits. Again, with UOA’s, the correct mentality is to establish acceptable wear limits, and run your oil out to the full term. If you do this, you don’t get less wear with synthetic and/or bypass filtration, you get more life cycle of the fluid. The reason synthetics and bypass filtration can show better numbers at the same OCI is because they are more capable. But it’s an unfair comparison. The goal is to limit wear, not OCI duration. It’s no different than asking one person to run 40 yards and measure them in seconds (time as a variable), but then tell the next person to run for 40 seconds and see how many yards they run (distance as a variable)! You have changed the fixed and variable metrics!
There is a side-line issue of synthetics being more, shall we say, temperature capable. That’s true, but only in a very narrow context. For cold weather, synthetics only offer a significant advantage below -15 deg F or so. But how many of us really operate in such an environment for much duration, if ever? Some do, but they are a very small minority. Further, what about heat protection? Presuming your cooling system is working correctly, conventional oils do just fine. Synthetics would only protect better if an overheated condition were to exist, and only for a limited time. As the temp rises quickly, there is a very small window of opportunity for the synthetic to succeed where the conventional would fail. After that window closes, any oil would fail, regardless of group composition. It is also true that synthetics resist evaporation somewhat better than conventional oils, but does that make the engine better protected? No, it simply means the synthetic oil lasts longer. The make-up oil is a consideration of cost, not wear.
Now, I’m sure that some of you might still be in the “Yeah, but …” camp. Well, I don’t know that I’ll ever be able to convince you otherwise; nor would you be able to convince me. We will have to agree to disagree. But in my mind, given the intent of wear analysis, synthetics and bypass filtration make fluids last longer, not equipment. If you don't run up to your established acceptable limits, you're cheating the fluid, and your wallet. And if you do run up to the acceptable limits, then wear is the same, and the return is in fluid life cycle; equipment life cycle is the same.
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