And don't forget the long-term wear effect due to oil degradation from cold shut downs. When you fire up the engine, move the car out the driveway to let someone out, and back in, then shut it off. You leave all those contaminants in the crankcase to soak into the oil. Cold shutdowns may be a significant wear factor that, insofar as the oil is permanently degraded, extend throughout hot running conditions.
Cold Start Wear
- Thread starter Blue99
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There's actually been quite a few studies on this subject. In one study I read, they normalized wear to fresh oil and steady state highway speeds. During a cold start event, insufficient lube resulted in 100-500 miles of wear. And another 100-500 miles of wear was due to unburnt hydrocarbons which aggregate while the oil is cold and some is due to acidic attack of the engine metal due to oxidation of the oil and hydrobromic acids which aren't boiled off until the engine is warmed above 140F.
The above is why it's preferable not to idle an engine up to temperature. It's much better to drive gently once the oil reaches all the vital areas as it warms the engine up quicker.
Very interesting! I would like to ask: What has to be warmed above 140F? Surely not the coolant, as that is never (barring various gasket leaks) in contact with combustion by-products nor oil. Does the oil have to reach 140F? Does the metal at the surface of the piston/cylinder/cc? Surely those surfaces will heat above 140F very quickly being exposed to several-hundred-degree (even 1000F?) temps every other revolution. Could you expand a bit for me?
The coolant. Even in a fully warmed engine under load, the piston and rings surface thin oil films only reach about 360-570F and the thicker liner oil film is around 175-250F.
They don't have to be. Every oil (even newer formulas of the same brand/weight) has different characteristics. Then there's shearing down and/or thickening with use.
The sample point for 5W/10W is sub-freezing. What happens on the way to operating temperature could vary, but probably wouldn't make an appreciable difference in startup wear.
Very little, oil clings to metalic stuff rather well, and is rather viscous at startup and for the couple of seconds it takes for oil pressure to rise and oil to start flowing. Thin oil helps a lot here.
Again, I would say somewhat little.
A large part of the startup wear comes from the acidic byproducts of buring gasoline in a confinded cylinder. These acids attack the cylinder bors, rings, exhaust valve seats and exhaust ports. One the car is warm (all the way through the exhaust system), the acids remain as vapors and pass entirely through the system with little damage.
So, the acids are present and condense on cooler surfaces, the oil is thick and not flowing very fast and the acid inhibitors (TBN) are not working as well as when the oil is fully up to temp. This all adds up to opportunities for unprotected surfaces to get attacked.
Actually, I didn’t mention viscosity in my initial post, and was attempting to get beyond the endless “my favorite multi-grade vs. yours” debate.
My intention was to discuss the issue of cold start-up wear and if it can be eliminated thru the choice of lubricant in the crankcase.
Here’s a statement from the Castrol GTX Start-Up Product Data Sheet :
Castrol GTX Start Up is a motor oil that is specially formulated to provide superior start up protection. The rate of engine wear is higher during the first 10 minutes of each trip. Superior protection during these critical minutes after start up helps prevent engine wear, and potentially provides longer engine life.
Note the use of the phrases “helps prevent engine wear” and “potentially provides longer engine life”. Castrol is not claiming to eliminate start-up wear, only a reduction in the amount.
Now, here’s another statement from an Engine Oil Additive firm (Not a BITOG sponsor):
"When you start your engine in the morning, it runs for up to 60 seconds on the oil film left from the night before. Scientific studies in operating engines have shown that the wear rates are close to 50 times greater during starting than during running."
In addition, this engine oil additive firm claims the product “Eliminates harmful cold starts”.
Does anyone share the viewpoint that it is possible to eliminate all cold start wear?
My intention was to discuss the issue of cold start-up wear and if it can be eliminated thru the choice of lubricant in the crankcase.
Here’s a statement from the Castrol GTX Start-Up Product Data Sheet :
Castrol GTX Start Up is a motor oil that is specially formulated to provide superior start up protection. The rate of engine wear is higher during the first 10 minutes of each trip. Superior protection during these critical minutes after start up helps prevent engine wear, and potentially provides longer engine life.
Note the use of the phrases “helps prevent engine wear” and “potentially provides longer engine life”. Castrol is not claiming to eliminate start-up wear, only a reduction in the amount.
Now, here’s another statement from an Engine Oil Additive firm (Not a BITOG sponsor):
"When you start your engine in the morning, it runs for up to 60 seconds on the oil film left from the night before. Scientific studies in operating engines have shown that the wear rates are close to 50 times greater during starting than during running."
In addition, this engine oil additive firm claims the product “Eliminates harmful cold starts”.
Does anyone share the viewpoint that it is possible to eliminate all cold start wear?
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