What tweaked me: Somebody referred to the “Taxicab Study” once again to defend the use of thicker oils on a recent thread.
So I Think it is time to bring this up again, From:
Effect of Lubricant Properties and Lubricant Degradation on Piston Ring and Cylinder Bore Wear in a Spark-Ignition Engine, Schneider et al.
www.sae.org
First some definitions are important. Most automotive engine research uses the term Cold Engine to mean room temperature, 70-75F. It is not some freezing temperature. People may admit that engine wear is accelerated at cooler temperatures but they think it is below freezing, that is probably far worse. So when the reasearch paper makes a statement as the wear rate is more when the engine is cold they mean at room temperature.
The definition of warm up period. It is the time it takes for the oil to reach the steady state operating temperature. It occurs much slower than the heating of the coolant. Under high load it is usually at least a 15 minute period and slowly rises over this time from the room temperature “cold” start.
Once reached, the steady state oil temperature was regulated to 248F. The engines were varied. There was low load and varying RPM and high load and varying RPM.
Fully formulated oils were used except where the ZDDP level was formulated to be zero.
This research is made more relevant by actually using V-6 engines for wear testing - 1999 GM 3.4-L 60 degree block. And the radiotracer method of wear detection has been shown to be very accurate. No need for a tear down that is actually less accurate unless very long and hard engine use is forced. This study is for cylinder and ring wear, the location where most engines fail if properly manufactured and maintained. I believe most working engines are retired (or rebuilt) because of low compression. And sometimes without replacement of the bearings. The author states that cylinder wear and ring wear are perhaps the best areas to test oil and wear for engine longevity. Note this is in vivo testing, not some 4 ball lab test.
Conclusions, and there were a handful as this was a very far reaching study:
Steady state wear is very low except when changing to high load and RPM conditions, the rise is moderate. I think they used the word insignificant for wear at steady state and low loads.
Lubricants ranging from SAE 0W10 to SAE 10W40 had similar rates of wear (their wording, not mine). In the text they stated there was no trend in wear rates related to viscosity.
Lubricants that were aged with 16,000 normally driven miles were compared to fresh lubricants and had similar rates of wear. (There are some people who show evidence that fresh new oil can result in more wear than with older oil in your engine).
Fully formulated synthetic and mineral based lubricants had similar rates of wear.
When a hot, loaded running engine, is artificially cooled by gradually lowering the coolant and engine oil temperature from the steady state operating temperature to room temperature the wear rates gradually go up at the same rate. They end up being 10x higher at room temperature. Mind you it is still not that high overall. Let me digress. If something is said to be 10x worse you have to know the exact context. For example: If some medication causes an adverse effect that goes from 1 in 10M to 10 in 10M it is still very low. Even though it is 10X worse making it sound really, really bad. But if the adverse effect goes from 1 in 100 people to 10/100 people - Houston, we have a problem. So a statement saying that something is 10x better or 10x worse is meaningless without further explanation.
I find this really interesting: Wear rates were “only” 2x higher when the same oil had the ZDDP completely removed from the fully formulated oil - levels were originally at 0.10% ZDDP.
Wear is related to RPM and load. Load makes a much larger difference than RPM. Wear is 6 to 10X higher with increasing load and RPM. But again, the actual amount of wear is still considered low. Once the steady state oil temperature is reached the wear rate is almost nothing for the low load condition at 2000 RPM.
I did have discussions with Dr. Schneider regarding this research.
This thread was written with permission from Dr. Eric Schneider.
FYI: I will discuss the “Taxi Test” next. Many people refer to this study.
ali
So I Think it is time to bring this up again, From:
Effect of Lubricant Properties and Lubricant Degradation on Piston Ring and Cylinder Bore Wear in a Spark-Ignition Engine, Schneider et al.
Effect of Lubricant Properties and Lubricant Degradation on Piston Ring and Cylinder Bore Wear in a Spark-Ignition Engine
A radiotracer method was developed to measure real-time wear rates of piston rings and cylinder bores in spark-ignition engines. Initial work determined baseline wear rates during break-in and steady-state operating conditions. This work examines the effects of lubricant properties on wear rates of
First some definitions are important. Most automotive engine research uses the term Cold Engine to mean room temperature, 70-75F. It is not some freezing temperature. People may admit that engine wear is accelerated at cooler temperatures but they think it is below freezing, that is probably far worse. So when the reasearch paper makes a statement as the wear rate is more when the engine is cold they mean at room temperature.
The definition of warm up period. It is the time it takes for the oil to reach the steady state operating temperature. It occurs much slower than the heating of the coolant. Under high load it is usually at least a 15 minute period and slowly rises over this time from the room temperature “cold” start.
Once reached, the steady state oil temperature was regulated to 248F. The engines were varied. There was low load and varying RPM and high load and varying RPM.
Fully formulated oils were used except where the ZDDP level was formulated to be zero.
This research is made more relevant by actually using V-6 engines for wear testing - 1999 GM 3.4-L 60 degree block. And the radiotracer method of wear detection has been shown to be very accurate. No need for a tear down that is actually less accurate unless very long and hard engine use is forced. This study is for cylinder and ring wear, the location where most engines fail if properly manufactured and maintained. I believe most working engines are retired (or rebuilt) because of low compression. And sometimes without replacement of the bearings. The author states that cylinder wear and ring wear are perhaps the best areas to test oil and wear for engine longevity. Note this is in vivo testing, not some 4 ball lab test.
Conclusions, and there were a handful as this was a very far reaching study:
Steady state wear is very low except when changing to high load and RPM conditions, the rise is moderate. I think they used the word insignificant for wear at steady state and low loads.
Lubricants ranging from SAE 0W10 to SAE 10W40 had similar rates of wear (their wording, not mine). In the text they stated there was no trend in wear rates related to viscosity.
Lubricants that were aged with 16,000 normally driven miles were compared to fresh lubricants and had similar rates of wear. (There are some people who show evidence that fresh new oil can result in more wear than with older oil in your engine).
Fully formulated synthetic and mineral based lubricants had similar rates of wear.
When a hot, loaded running engine, is artificially cooled by gradually lowering the coolant and engine oil temperature from the steady state operating temperature to room temperature the wear rates gradually go up at the same rate. They end up being 10x higher at room temperature. Mind you it is still not that high overall. Let me digress. If something is said to be 10x worse you have to know the exact context. For example: If some medication causes an adverse effect that goes from 1 in 10M to 10 in 10M it is still very low. Even though it is 10X worse making it sound really, really bad. But if the adverse effect goes from 1 in 100 people to 10/100 people - Houston, we have a problem. So a statement saying that something is 10x better or 10x worse is meaningless without further explanation.
I find this really interesting: Wear rates were “only” 2x higher when the same oil had the ZDDP completely removed from the fully formulated oil - levels were originally at 0.10% ZDDP.
Wear is related to RPM and load. Load makes a much larger difference than RPM. Wear is 6 to 10X higher with increasing load and RPM. But again, the actual amount of wear is still considered low. Once the steady state oil temperature is reached the wear rate is almost nothing for the low load condition at 2000 RPM.
I did have discussions with Dr. Schneider regarding this research.
This thread was written with permission from Dr. Eric Schneider.
FYI: I will discuss the “Taxi Test” next. Many people refer to this study.
ali
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