How the engines run rougher with low oil?
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I'll take a stab at it.
Lower oil levels mean more friction. More friction brings heat and wear. Oil acts as a cooling agent, especially in air cooled engines. And if there isn't enough of it, I'd assume the engine internals could eventually weld itself and cease.
Lower oil levels mean more friction. More friction brings heat and wear. Oil acts as a cooling agent, especially in air cooled engines. And if there isn't enough of it, I'd assume the engine internals could eventually weld itself and cease.
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Basically it means less oil is able to be cycled through the engine. Less oil means it reaches extreme temperatures faster, reducing the capability of the oil to cope with the needs of the engine.
Oil will still flow the same up to an extent(meaning if you have barely any oil in, it may not even pump). It's just the less of it is there is, the faster the oil is going to be cycled not giving it ample enough time to cool down, be filtered etc.
Oil will still flow the same up to an extent(meaning if you have barely any oil in, it may not even pump). It's just the less of it is there is, the faster the oil is going to be cycled not giving it ample enough time to cool down, be filtered etc.
Once you lose oil to the HLAs the lifters aren't as effective and you get more rattling and less compression. This isn't really a point you want to reach: When you high high RPMs with oil this low you'll get starvation in the bearings and blow the motor.
gathermewool
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I've been running my engine with low oil for years now with out a problem. Having to keep proper level is like having to change it every year; just a myth.
If you saw an oil line coming from the pan it's either a dry sump setup used in race engines or an oil line for a turbo or supercharger, also for racing .The "rough running" you describe maybe mistaken for a really hot(lumpity-lump)cam.Look up 'dry sump' on a racing site to compare what you saw.
The oil level doesn't directly affect how the engine runs UNTIL the level gets low enough that air begins to get sucked into the oil pickup tube, and then things go REALLY bad really fast. If you think you're observing "rougher running" with the engine just a little low on oil, you're just convincing yourself its true.
As for higher temperatures- yes, that CAN happen even with just a quart low because there's less reservoir volume and the same oil has to go through the engine more often, spending less time in the pan to cool off. But in normal or even moderately hard driving that won't affect the measurable performance of the engine unless its a Nissan with a 3-quart sump.
As for higher temperatures- yes, that CAN happen even with just a quart low because there's less reservoir volume and the same oil has to go through the engine more often, spending less time in the pan to cool off. But in normal or even moderately hard driving that won't affect the measurable performance of the engine unless its a Nissan with a 3-quart sump.
Yeah it's a vicious cycle. Less oil and it is can run hotter and become thinner. So you are pumping more of it and if the oil level is too low and at highway speeds you can suck the pan dry. It happened to some early Fieros with a 2.5, before they increased the oil fill capacity 1 qt. You had like 3 qts capacity with the filter in the pan on a mid-engine vehicle. People would run them a qt or 2 low or who knows and with a fairly low gear and a 3 speed automatic some of them threw a rod and even caught on fire, fiberglass plastic body panels.
But this was an almost worse case scenario. The 2.5 could tend to leak lose some oil from the valve cover,and mid-engine fiero's could run a little hot. And the multigrade oil in the mid-late 80's, probably was pretty volatile and so it wasn't hard to get a quart or 2 low if you didn't check/change your oil regularly. But about all it took was an extra qt to aleviate the issue.
But this was an almost worse case scenario. The 2.5 could tend to leak lose some oil from the valve cover,and mid-engine fiero's could run a little hot. And the multigrade oil in the mid-late 80's, probably was pretty volatile and so it wasn't hard to get a quart or 2 low if you didn't check/change your oil regularly. But about all it took was an extra qt to aleviate the issue.
Originally Posted By: FL_Rob
If you saw an oil line coming from the pan it's either a dry sump setup used in race engines or an oil line for a turbo or supercharger, also for racing .The "rough running" you describe maybe mistaken for a really hot(lumpity-lump)cam.Look up 'dry sump' on a racing site to compare what you saw.
This is most likely what was observed - you beat me to it.
In a normal engine, many parts are lubricated by plain old splash, and being very low on oil would starve them of lube, hence a roughness/drag could occur.
If you saw an oil line coming from the pan it's either a dry sump setup used in race engines or an oil line for a turbo or supercharger, also for racing .The "rough running" you describe maybe mistaken for a really hot(lumpity-lump)cam.Look up 'dry sump' on a racing site to compare what you saw.
This is most likely what was observed - you beat me to it.
In a normal engine, many parts are lubricated by plain old splash, and being very low on oil would starve them of lube, hence a roughness/drag could occur.
What you're describing sounds like my car ALL THE TIME.
When I'm running on the highway, I feel the car pull back a bit every now and then. Like it has a miss, but it doesn't.
When I stop after a highway run and idle into my driveway, it's almost like I can hear the air sucking up the oil pickup screen. A real hollow "death rattle" like sound. But there's no metal sounds or anything, no knocks, just that incessant TICKYTACKY rocker arm clack.
When I'm running on the highway, I feel the car pull back a bit every now and then. Like it has a miss, but it doesn't.
When I stop after a highway run and idle into my driveway, it's almost like I can hear the air sucking up the oil pickup screen. A real hollow "death rattle" like sound. But there's no metal sounds or anything, no knocks, just that incessant TICKYTACKY rocker arm clack.
It does make sense. I can't tell you how many times I've simply listened to an engine, say my neighbors, friends or "others" and would tell them that I'd bet them money the engine is low on oil. Sure enough, 9 out ot 10 times I was correct, they were usually at least a quart low. It just bugs the heck out of me how in the world they couldn't hear it or even thought about checking the oil or asking someone to take a look at it if it didn't just sound "right". I know farmers are pros at this.
Originally Posted By: mechtech2
Originally Posted By: FL_Rob
If you saw an oil line coming from the pan it's either a dry sump setup used in race engines or an oil line for a turbo or supercharger, also for racing .The "rough running" you describe maybe mistaken for a really hot(lumpity-lump)cam.Look up 'dry sump' on a racing site to compare what you saw.
This is most likely what was observed - you beat me to it.
In a normal engine, many parts are lubricated by plain old splash, and being very low on oil would starve them of lube, hence a roughness/drag could occur.
No modern engine oils by splash *from the pan*. Anything that is "splash" lubricated is lubricated by spray that originated from the pressurized part of the oiling system- such as cylinder walls being "splashed" by spray from the bearing clerances and connecting rod squirt holes. That's why modern engines have windage trays- specifically to PREVENT moving parts "splashing" the oil in the sump at all.
So long as the pickup tube is submerged, the engine won't know or care if the sump is completely full or 2 quarts low, and there will not be any difference, audible or otherwise, in the way the engine runs. But the minute the pickup starts sucking air, all bets are off.
Originally Posted By: FL_Rob
If you saw an oil line coming from the pan it's either a dry sump setup used in race engines or an oil line for a turbo or supercharger, also for racing .The "rough running" you describe maybe mistaken for a really hot(lumpity-lump)cam.Look up 'dry sump' on a racing site to compare what you saw.
This is most likely what was observed - you beat me to it.
In a normal engine, many parts are lubricated by plain old splash, and being very low on oil would starve them of lube, hence a roughness/drag could occur.
No modern engine oils by splash *from the pan*. Anything that is "splash" lubricated is lubricated by spray that originated from the pressurized part of the oiling system- such as cylinder walls being "splashed" by spray from the bearing clerances and connecting rod squirt holes. That's why modern engines have windage trays- specifically to PREVENT moving parts "splashing" the oil in the sump at all.
So long as the pickup tube is submerged, the engine won't know or care if the sump is completely full or 2 quarts low, and there will not be any difference, audible or otherwise, in the way the engine runs. But the minute the pickup starts sucking air, all bets are off.
Originally Posted By: Schmoe
It does make sense. I can't tell you how many times I've simply listened to an engine, say my neighbors, friends or "others" and would tell them that I'd bet them money the engine is low on oil. Sure enough, 9 out ot 10 times I was correct, they were usually at least a quart low.
There's a simple explanation for that: nobody checks their own oil on the road anymore and 9 out of 10 of ALL cars are low on oil. If you walked up to a random car in the parking lot at a mall, with the engine off, and said "it sounds like it's a quart low" and then checked it, 9 out of 10 times you'd be right.
It does make sense. I can't tell you how many times I've simply listened to an engine, say my neighbors, friends or "others" and would tell them that I'd bet them money the engine is low on oil. Sure enough, 9 out ot 10 times I was correct, they were usually at least a quart low.
There's a simple explanation for that: nobody checks their own oil on the road anymore and 9 out of 10 of ALL cars are low on oil. If you walked up to a random car in the parking lot at a mall, with the engine off, and said "it sounds like it's a quart low" and then checked it, 9 out of 10 times you'd be right.
440 - The cam and pistons are splash lubricated. And so are the piston pins. Add valve/valve guides to this list
How about a cam chain?
C'mon now...
How about a cam chain?
C'mon now...
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We have cars come into our shop for oil changes and if we're lucky, 1.5 quarts will drain from the pan. Its mind boggling how people don't care, can't even check their own oil.
Originally Posted By: mechtech2
440 - The cam and pistons are splash lubricated. And so are the piston pins. Add valve/valve guides to this list
How about a cam chain?
C'mon now...
None of those parts are lubricated by what I would call splash. Let me clarify- to me "splash" lubrication is like a rear-end gear is lubricated- rotating parts physically DIP into the oil standing in the sump and then fling the oil to other places. That doesn't happen in a car engine, at least not since the mid 50s
In the case of the pistons, the valves, guides, and timing chain- oil is PUMPED to all of those locations in one way or another, NOT by the crank dipping in the sump. Take the undersides of the pistons and the wrist-pin for example: oil is picked up by the pump, filtered, fed through the oil galleries to the crank, through the crank to the rod bearing journals, and from there it is sprayed out the rod bearing clearance (or piston squirt holes) and flung onto the underside of the piston by the rotation of the crank. At no point in there does the crank depend on dipping into the oil. Same for all the others- valve gear is lubricated either through the pushrods or rocker arm shafts by oil that is pumped there through the galleries. The cam chain is lubed by squirters from pressurized oil galleries, either a notch in the #1 cam bearing or a rifle-drilled bolt into an oil gallery, etc.
Because nothing dips into the sump oil, the oil level doesn't really matter to lubrication other than to keep the pickup submerged. That's why any modern car engine can easily be converted to a dry sump system if you want to.
To take it a step further, even if you fill the sump completely full on a modern car engine, it will seize up in no time and *nothing* in it will get oil if the oil pump isn't working since the oil in the sump won't move at all.
A lawnmower engine is lubricated by splash, not a car engine (at least not since the last "stovebolt" Chevy six rolled off the line in the 50s- it still had dippers on the crank). Heck, many lawnmower engines aren't even splash-lubed anymore.
440 - The cam and pistons are splash lubricated. And so are the piston pins. Add valve/valve guides to this list
How about a cam chain?
C'mon now...
None of those parts are lubricated by what I would call splash. Let me clarify- to me "splash" lubrication is like a rear-end gear is lubricated- rotating parts physically DIP into the oil standing in the sump and then fling the oil to other places. That doesn't happen in a car engine, at least not since the mid 50s
In the case of the pistons, the valves, guides, and timing chain- oil is PUMPED to all of those locations in one way or another, NOT by the crank dipping in the sump. Take the undersides of the pistons and the wrist-pin for example: oil is picked up by the pump, filtered, fed through the oil galleries to the crank, through the crank to the rod bearing journals, and from there it is sprayed out the rod bearing clearance (or piston squirt holes) and flung onto the underside of the piston by the rotation of the crank. At no point in there does the crank depend on dipping into the oil. Same for all the others- valve gear is lubricated either through the pushrods or rocker arm shafts by oil that is pumped there through the galleries. The cam chain is lubed by squirters from pressurized oil galleries, either a notch in the #1 cam bearing or a rifle-drilled bolt into an oil gallery, etc.
Because nothing dips into the sump oil, the oil level doesn't really matter to lubrication other than to keep the pickup submerged. That's why any modern car engine can easily be converted to a dry sump system if you want to.
To take it a step further, even if you fill the sump completely full on a modern car engine, it will seize up in no time and *nothing* in it will get oil if the oil pump isn't working since the oil in the sump won't move at all.
A lawnmower engine is lubricated by splash, not a car engine (at least not since the last "stovebolt" Chevy six rolled off the line in the 50s- it still had dippers on the crank). Heck, many lawnmower engines aren't even splash-lubed anymore.
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