The hone holds the oil so that the rings can ride on the hydrodynamic film and the oil left behind is then burned in the combustion process. It is design intent, but unlike wankels and 2 stroke engines the amount of oil needed is greatly reduced.
Oil Consumption by Design
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If I remember correctly it was General Motors who first advanced the statement that one quart of oil per 1,000 miles was normal. Ed
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Originally Posted By: KrisZ
The hone holds the oil so that the rings can ride on the hydrodynamic film and the oil left behind is then burned in the combustion process. It is design intent, but unlike wankels and 2 stroke engines the amount of oil needed is greatly reduced.
The primary purpose of the hone is to bed the rings for proper ring seal. The secondary purpose is, as you indicated, to aide in holding some oil film to the cylinder wall. Depending on ring tension, piston height and scrub angle, will dictate how much of the hone on the thrust face of the cylinder is removed.
I've torn down many high, HIGH mileage SBF's with what looks like a full hone completely intact (short stroke, big bore, tall piston) whereas I've torn down a few SBC's where there's no hone to be seen on the front or back of the cylinder, only on the sides.
The hone holds the oil so that the rings can ride on the hydrodynamic film and the oil left behind is then burned in the combustion process. It is design intent, but unlike wankels and 2 stroke engines the amount of oil needed is greatly reduced.
The primary purpose of the hone is to bed the rings for proper ring seal. The secondary purpose is, as you indicated, to aide in holding some oil film to the cylinder wall. Depending on ring tension, piston height and scrub angle, will dictate how much of the hone on the thrust face of the cylinder is removed.
I've torn down many high, HIGH mileage SBF's with what looks like a full hone completely intact (short stroke, big bore, tall piston) whereas I've torn down a few SBC's where there's no hone to be seen on the front or back of the cylinder, only on the sides.
Originally Posted By: KrisZ
All engines have to consume oil, all of them, but the normal amount, on a healthy engine with properly broken in and not stuck piston rings, will not be noticeable on the dipstick or the change in the level should be minimal.
...
And low tension piston rings are nothing new, it's just something people like to repeat to convince themselves and others that it is normal. You repeat it enough times and it becomes the truth.
I agree, and therefore have doubts about some of the popular theories above.
Advertising and press-release fluff in 1980 for my '81 Mazda bragged about its low-tension rings (among other fuel-saving then-new features). My current car, the Prius, also claims low-tension rings, uses 0W-20 (sometimes 5W-20), yet so far consumes far less oil than any other engine with which I've been acquainted. How is that possible if low-tension rings and "watery" oil necessarily cause high oil consumption? Some Prii with the same engine design reportedly do guzzle oil after they've accumulated a few miles, but the reasons that happens are a semi-separate issue.
All engines have to consume oil, all of them, but the normal amount, on a healthy engine with properly broken in and not stuck piston rings, will not be noticeable on the dipstick or the change in the level should be minimal.
...
And low tension piston rings are nothing new, it's just something people like to repeat to convince themselves and others that it is normal. You repeat it enough times and it becomes the truth.
I agree, and therefore have doubts about some of the popular theories above.
Advertising and press-release fluff in 1980 for my '81 Mazda bragged about its low-tension rings (among other fuel-saving then-new features). My current car, the Prius, also claims low-tension rings, uses 0W-20 (sometimes 5W-20), yet so far consumes far less oil than any other engine with which I've been acquainted. How is that possible if low-tension rings and "watery" oil necessarily cause high oil consumption? Some Prii with the same engine design reportedly do guzzle oil after they've accumulated a few miles, but the reasons that happens are a semi-separate issue.
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Originally Posted By: CR94
Originally Posted By: KrisZ
All engines have to consume oil, all of them, but the normal amount, on a healthy engine with properly broken in and not stuck piston rings, will not be noticeable on the dipstick or the change in the level should be minimal.
...
And low tension piston rings are nothing new, it's just something people like to repeat to convince themselves and others that it is normal. You repeat it enough times and it becomes the truth.
I agree, and therefore have doubts about some of the popular theories above.
Advertising and press-release fluff in 1980 for my '81 Mazda bragged about its low-tension rings (among other fuel-saving then-new features). My current car, the Prius, also claims low-tension rings, uses 0W-20 (sometimes 5W-20), yet so far consumes far less oil than any other engine with which I've been acquainted. How is that possible if low-tension rings and "watery" oil necessarily cause high oil consumption?
Nobody has said (obviously that it does so in all occasions...ever seen one of these ?
The OEMs are defining "normal"...note, it's THEIR definition at the tail end of the curve.
Originally Posted By: KrisZ
All engines have to consume oil, all of them, but the normal amount, on a healthy engine with properly broken in and not stuck piston rings, will not be noticeable on the dipstick or the change in the level should be minimal.
...
And low tension piston rings are nothing new, it's just something people like to repeat to convince themselves and others that it is normal. You repeat it enough times and it becomes the truth.
I agree, and therefore have doubts about some of the popular theories above.
Advertising and press-release fluff in 1980 for my '81 Mazda bragged about its low-tension rings (among other fuel-saving then-new features). My current car, the Prius, also claims low-tension rings, uses 0W-20 (sometimes 5W-20), yet so far consumes far less oil than any other engine with which I've been acquainted. How is that possible if low-tension rings and "watery" oil necessarily cause high oil consumption?
Nobody has said (obviously that it does so in all occasions...ever seen one of these ?
The OEMs are defining "normal"...note, it's THEIR definition at the tail end of the curve.
VW, older Volvo's, Saab, Audi, and my wifes Jag XJ6 all burn about 1 qt per 1,000 miles. I have had examples of all of these and they all went well beyond 200,000 miles w/o much needed.
My wife's Jag has 187,000 on it now and passes SMOG with flying colors. It did loose a head gasket at 117,000 and got a valve job because we were already in that far anyway. Other than that the engine just keeps on keepin on.
It's usually related to either low tension rings (but not in the examples above) or slightly larger ring end gaps and some play in the valve guides with minimal valve stem sealing. As long as the oil consumed does not overwhelm the CAT, there is no down side.
All my hot rodded engines burn some oil. The race motors don't run any valve stem seals at all so they will always puff a bit on start-up. Oil is cheap. Rings closing the end gaps and seizing are not ...
My wife's Jag has 187,000 on it now and passes SMOG with flying colors. It did loose a head gasket at 117,000 and got a valve job because we were already in that far anyway. Other than that the engine just keeps on keepin on.
It's usually related to either low tension rings (but not in the examples above) or slightly larger ring end gaps and some play in the valve guides with minimal valve stem sealing. As long as the oil consumed does not overwhelm the CAT, there is no down side.
All my hot rodded engines burn some oil. The race motors don't run any valve stem seals at all so they will always puff a bit on start-up. Oil is cheap. Rings closing the end gaps and seizing are not ...
Originally Posted By: ShieldArc
I'm still wondering why the 8.1 in my 2001 3500HD has used 1qt every 750 mi since new no matter what oil I put in it.
I have the Mercruiser (GM) 8.1's in my Searay and experienced oil consumption - although within the limits of consumption as per the handbook. Last year I swapped out the Merc 25W/40 and filled it with Penrite Racing 10 tenths 15W/50. Although there is still some consumption I haven't had to top it up, unlike the Merc oil where I had to top it up from time to time. I've heard similar results with the M1 15w/50.
I'm still wondering why the 8.1 in my 2001 3500HD has used 1qt every 750 mi since new no matter what oil I put in it.
I have the Mercruiser (GM) 8.1's in my Searay and experienced oil consumption - although within the limits of consumption as per the handbook. Last year I swapped out the Merc 25W/40 and filled it with Penrite Racing 10 tenths 15W/50. Although there is still some consumption I haven't had to top it up, unlike the Merc oil where I had to top it up from time to time. I've heard similar results with the M1 15w/50.
Originally Posted By: Shannow
... Nobody has said (obviously that it does so in all occasions...ever seen one of these ?
The OEMs are defining "normal"...note, it's THEIR definition at the tail end of the curve.
...
Ever seen a bimodal distribution? That would be a little closer to reality here than your simple normal distribution "bell curve." To save warranty costs, OEM's are redefining sick engines as normal.
... Nobody has said (obviously that it does so in all occasions...ever seen one of these ?
The OEMs are defining "normal"...note, it's THEIR definition at the tail end of the curve.
...
Ever seen a bimodal distribution? That would be a little closer to reality here than your simple normal distribution "bell curve." To save warranty costs, OEM's are redefining sick engines as normal.
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