The only startup wear to worry about is when a straight 30 wt is used in 0 degrees f. "for example"
Pressure vs Flow Regarding Wear Revisited
- Thread starter AEHaas
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Maybe they want a lesser film thickness than is needed during break in to help smooth the surfaces.
The usual recommendation for older cars break in is a 30wt oil and then a 20W50.
Castrol especially with start up advertising indicate an additive activation period.
The usual recommendation for older cars break in is a 30wt oil and then a 20W50.
Castrol especially with start up advertising indicate an additive activation period.
Effect of Break-In and Operating Conditions on Piston Ring and Cylinder Bore Wear in SI (Spark-Ignition) Engines, Schneider et al.
Effect of Lubricant Properties and Lubricant Degradation on Piston Ring and Cylinder Bore Wear in a Spark-Ignition Engine, Schneider et al.
Some people may have missed these. Check the citation index and you will see how well received these papers have been. The first shows the best study in my mind regarding wear and temperature. From an earlier analysis of mine:
The rate of wear is much higher within 15-20 minutes of start-up than after reaching normal operating temperature. There was a lot of data but I conclude that the initial start-up time period (first 20 minutes) result is 100 nanometers of wear whereas the steady state wear rate was only 4 nanometers per hour thereafter. (Hence we should be concerned about start-up oil thickness more than running thickness. This justifies the statement that 95 percent of engine wear occurs just after start-up).
My previously published review of the second article:
Most interesting to me was the way they tested wear at lower, start up, oil temperatures. In a previous study (1) they start with room temperature engines and oil showing the trend of decreasing wear as the engine heated up. In the current study they actually took a hot engine and chilled the coolant and oil from that of the normal operating temperature to a coolant temperature of around 80 F and oil temperature to 70 F. As the temperatures fell the wear increased. It reached the same rate of wear as the 4,000 RPM full load WOT. This was with the load at the minimum level. The fluids were then allowed to heat back up to normal operating temperatures and the wear rates normalized (decreased).
You guys who have not read these full articles should do so NOW.
aehaas
FYI: Dr. Eric Schneider does most of the oil research for GM. He is currently working on more start up related oil analysis and I mean at STP, room temperature, not at freezing temperatures. New, more every day, room temperature experiments are forthcoming within the next year. This area of higher engine wear has stimulated Dr. Schneider’s interest level.
Effect of Lubricant Properties and Lubricant Degradation on Piston Ring and Cylinder Bore Wear in a Spark-Ignition Engine, Schneider et al.
Some people may have missed these. Check the citation index and you will see how well received these papers have been. The first shows the best study in my mind regarding wear and temperature. From an earlier analysis of mine:
The rate of wear is much higher within 15-20 minutes of start-up than after reaching normal operating temperature. There was a lot of data but I conclude that the initial start-up time period (first 20 minutes) result is 100 nanometers of wear whereas the steady state wear rate was only 4 nanometers per hour thereafter. (Hence we should be concerned about start-up oil thickness more than running thickness. This justifies the statement that 95 percent of engine wear occurs just after start-up).
My previously published review of the second article:
Most interesting to me was the way they tested wear at lower, start up, oil temperatures. In a previous study (1) they start with room temperature engines and oil showing the trend of decreasing wear as the engine heated up. In the current study they actually took a hot engine and chilled the coolant and oil from that of the normal operating temperature to a coolant temperature of around 80 F and oil temperature to 70 F. As the temperatures fell the wear increased. It reached the same rate of wear as the 4,000 RPM full load WOT. This was with the load at the minimum level. The fluids were then allowed to heat back up to normal operating temperatures and the wear rates normalized (decreased).
You guys who have not read these full articles should do so NOW.
aehaas
FYI: Dr. Eric Schneider does most of the oil research for GM. He is currently working on more start up related oil analysis and I mean at STP, room temperature, not at freezing temperatures. New, more every day, room temperature experiments are forthcoming within the next year. This area of higher engine wear has stimulated Dr. Schneider’s interest level.
MolaKule
Staff member
I would think the wear curve would be an exponential decay (e-^x) from 100 nm to an asymptotic 4 nm, not a straight line.
So I am skeptic of the 96% start up wear for 20 minutes.
So I am skeptic of the 96% start up wear for 20 minutes.
"I would think the wear curve would be an exponential decay (e-^x) from 100 nm to an asymptotic 4 nm, not a straight line."
A good guess but if you read the article you will see why this is not the case. I cannot begin to go over everything the first article has to offer you. But, after the engine oil reaches approx. 200 F the wear rate stays at a steady 4 nm per hour. It is not asymptotic. Furthermore, if they stopped the engine for 10 minutes without letting it cool down the wear rate remains at exactly 4 nm per hour upon restart. It picks up right where it left off.
aehaas
A good guess but if you read the article you will see why this is not the case. I cannot begin to go over everything the first article has to offer you. But, after the engine oil reaches approx. 200 F the wear rate stays at a steady 4 nm per hour. It is not asymptotic. Furthermore, if they stopped the engine for 10 minutes without letting it cool down the wear rate remains at exactly 4 nm per hour upon restart. It picks up right where it left off.
aehaas
That being the case, why not put preoilers back into vehicles for start up? I realize that the oil would still be cold (less than optimal temperature), but wouldn't some form of lubricant already in the bearing area be a step toward lowering the wear rate from 100 nanometers at a full cold start until the oil reached full temperature? Or would the difference be so minute as to not warrant the extra cost and parts, as one is still not getting fully warmed up lubricant circulating right from the first crank?
"Normal operating temperature" of what?
The engine? The oil?
Water temp gets normal pretty quick and I believe is a good indicator that the engine is within the range of normal operating temperature, albeit the lower end of the range. Normal operating temp for the oil lags that of the water. Typically the water temp is reached in a few miles, but the oil takes maybe 15 miles. I maintain that it is the water temp that dictates the engine is warmed up.
...Getting back on track....
I have shown that oil flow is very important. I suggest that those interested in doing things to decrease wear in their engines should consider ways to increase oil flow. Consider ways to increase flow without unnecessary increases in pressure. Minimize parasitic losses from internal friction and heat production.
aehaas
I have shown that oil flow is very important. I suggest that those interested in doing things to decrease wear in their engines should consider ways to increase oil flow. Consider ways to increase flow without unnecessary increases in pressure. Minimize parasitic losses from internal friction and heat production.
aehaas
Other than a lighter oil...what else can one do besides major bolt on components?
""That being the case, why not put preoilers back into vehicles for start up"'
How about a hotter additve mix?
bruce
How about a hotter additve mix?
bruce
Bruce, define hotter? More of a good thing metallic wise, more organic compounds that are capable of exothermic reactions without reacting with the components of the engine, or should we all add hot sauce to our oil!?!
additves that react at lower temps ZDDP to me has always been a lousy AW additve compared to what we use in metalworking anyway.
bruce
bruce
I'm no engineer but shouldn't bearing displacement also be addressed. Wear may be fine with a thinner film but in that case couldn't a bearing lose center and cause other problems. I assume this is offset by the fact that engines are relatively balanced in their loads as some bearings see pressure on one side when others on the other and that their might be a wide acceptable visc but I'd like to hear what the experts have to say. I'm thinking that in some high performance apps a higher visc may make more power even if you lose some economy due to balance and maybe ring seal and that low visc may not always be win win even if wear is low.
Hmmm..Now you've got my interest perking up a bit. What types of compounds do you have in mind?
The missing link, smoking gun:
The anti wear additive that works best, the chemical Vmax, occurs at 75 F. Bruce is right on in my thinking.
aehaas
The anti wear additive that works best, the chemical Vmax, occurs at 75 F. Bruce is right on in my thinking.
aehaas
Thanks AEHaas. Can I just do a search to find out about it, or do you have a paper on this as well that I don't know about?
Here are conclusions from a research paper I got from 1995:
1. Lube temp on the bearing surface varies in proportion with feed oil temp (test engine showed rod bearing temp was 5 to 10C higher than oil temperature)
2. Temperature difference between bearing surface and feed oil is almost independent of engine load and viscosity, but quadratically increases with engine speed. (test engine shows the rod bearing was 5C hotter than the oil at 1000 rpm, 15C at 3000 rpm, 30C at 5000 rpm - near redline!)
3. Rod side bearing temperatures are higher than the cap side. (difference increases at higher rpm)
4. High temperature regions appear near the edges of the rod side bearing under high speed and wear occurs near the edges.
This indicates that flow is extremely important for cooling and should be treated just as important as pressure for the lubricanting film. Flow and pressure are closely related anyways.
1. Lube temp on the bearing surface varies in proportion with feed oil temp (test engine showed rod bearing temp was 5 to 10C higher than oil temperature)
2. Temperature difference between bearing surface and feed oil is almost independent of engine load and viscosity, but quadratically increases with engine speed. (test engine shows the rod bearing was 5C hotter than the oil at 1000 rpm, 15C at 3000 rpm, 30C at 5000 rpm - near redline!)
3. Rod side bearing temperatures are higher than the cap side. (difference increases at higher rpm)
4. High temperature regions appear near the edges of the rod side bearing under high speed and wear occurs near the edges.
This indicates that flow is extremely important for cooling and should be treated just as important as pressure for the lubricanting film. Flow and pressure are closely related anyways.
But the anti-wear additives are only needed when the hydrodynamic layer breaks down, correct? Let's face it, in an engine operating under normal loads at normal operating temps (both engine and oil temps), there is virtually zero wear going on at the bearings. ZDDP, moly, antimony, boron, over base calcium...that stuff is all there to do one thing: form a protective barrier between the metal parts when the oil itself can no longer provide that barrier (for whatever reason).
The sound of my main and rod bearings rattling on cold starts in my 300M was painful to listen to. I've lived with it for five years and would wince every time I'd turn the key and watch the tach needle swing to 1500 rpm and listen to that rattle for the split second it would take for the oil pressure to come up. No one can convince me that an inordinate amount of wear was not taking place in that split second. And this bearing rattle took place with 10w30, 5w30, and 5w20. It doesn't happen with straight 30. Does that mean that straight 30 protects better at start up? For my engine, under my current temp and driving conditions, I think it does. The real issue is why does it protect better. Obviously, 5w20 is going to flow faster at start up than the thicker straight 30. Is the 30 staying in the bearing surfaces where the 5w20 would migrate away and that's why there is no rattle with the 30? Is it because they both stay on the bearing surfaces, but the thicker 30 provides more hydrodynamic cushion at start up, when the oil is too cold for the AW and EP additives to activate and do any good? I don't know the answer. But I do know what my ears are telling me: No bearing rattle = less start up wear.
seems that when the block is cooled the bores decrease in diameter so the piston will be somewhat too big for the bore, as the piston gets hot quick and is expanded .There has to be more friction and so wear is higher. Cooling the oil may kick down the protection the antiwear adds give though seems there should be enough heat in the friction areas. I got into this years ago when building boat motors the hot piston cold block problem . Raw water cooling .
Eliminate the warm up and the wear will be decreases Again .Take two identical semi trucks run one semi coast to coast and the other semi around town doing pickup and deliveries and I will bet we can say which engine will have the higher miles before overhaul.
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