Ridge from syn oil?

Messages
25
Location
Jefferson, TX
Had a guy tell me that syn can form a ridge in a cylinder 'cause it doesn't burn off as easily as regular oil. Haven't seen any in several motorcycle engines I've torn into that were run on synthetic. Anybody else hear of/ see this?
 
Messages
1,967
Location
Kitsap, WA
At TDC and BDC the piston(and rings) stops, then switches direction. The lack of motion or speed makes for poor hydrodynamic oil film barrier. This area is wear or a ridge will occur. This is where the additives come into play to “catch” the lack of oil film. In short, if he’s seeing difference in oils, all other things being equal it is more likely an issue with the add pack then synthetic vs mineral basestock. Exception may be if the viscosity being used was way out of range (thin). Another may be glazing of the bore which I've seen with certain synthetics, in this case you might "feel" something like a ridge but it's not really into the metal and cleans right up with a light hone. If the mechanic swears what he's saying is valid, he should tell his customers to look at switching brands, whether it be syn or min.
 
Messages
234
Location
Scotts Valley, Ca.
pococj, First, I don't know what I'm typing about. It does seem to me though that this is counter intuitive. Having read here for a while the general opinion I have formed is thst the synthetics seem to yeild lower wear in general as I look at the UOA's. I tend to see less Fe (Iron) in the used oil when syn's are used. I also see that the use of FP-60, MMO, etc seem to lower the cyl wear when used to treat the top end. If any of the above is close to correct, and it seems to be from my results, I think that you may be being offered some poor suggestion here. If, as you have been advised that the syn's don't burn, then it seems that they should remain to assist in the lube of the top end. Why would this produce a larger ring-ridge than dino which is apparently supposed to burn off? In the "Old Days" the use of drip sysytems to add oil to the top end seemed to proove the value of lubricating above the piston. It seems to me that this may be a suggestion based on hear-say and not experiance. As you said, you haven't seen the evidence, so doubt the suggestion until you can see a way to verify it is my suggestion. John
 
Messages
3,479
Location
Millbrae, CA
wrong syn or otherwise ridges are from wear and since a syn is a higher boiling fraction it ought to be better at reduceing "ridge" formation guy is wrong. bruce
 
Messages
4,478
Location
Southern California
And here I always believed the ridge was unworn cylinder sleeve or block metal due to the top piston ring not "traveling" all the way to the top of the cylinder...
 
Messages
135
Location
Ramsey
I don't think I have ever seen a ridge at BDC. The ridge at TDC is caused by the force of the ignited fuel/air mixture pushing outward on the rings onto the cylinder walls. The rings naturally have a static spring pressure on the cylinder walls, but the pressure is increased dramatically at the point of ignition.
 
Messages
3,558
Location
SE Pa
A small wear ridge develops at the top of every cylinder given enough use. That's why we have "ridge reamers" (not cylinder hones) in the tool chest. You can't get the piston out of the bore normally otherwise. Oil has NOTHING to do with it. Deposits sometimes form a carbon ring at the cylinder top as well. Again, here we ream or hone it off before lifting the piston out. Your friend is likely referring to the latter if anything.
 

pococj

Thread starter
Messages
25
Location
Jefferson, TX
Thanks for the replies. The guy isn't a mechanic, just a guy who has brought up some rather strange points about synthetic oil use. For instance - (BEGIN QUOTE) I personally am not a fan of synthetic oils in an internal combustion engine for several reasons; 1) Usually costs 2 to 3 times as much as conventional oil. 2) The manufacturer recommendation. 3) Synthetic does not burn well. Burn well? you ask. Every stroke of an internal combustion engine leaves a light film of oil in the combustion chamber. With dino oil, this film is combusted. With synthetic, because it has "such great thermal properties", the oil glazes to the combustion chamber and forms a ridge over time. This ridge will reduce the combustion area in effect raising compression. Over time, the compression can become to high resulting in combustion gases blowing by the piston and rings into the crankcase. The increased pressure will eventually take its toll on the connecting rods, bearings, and crank resulting in premature engine failure and more frequent engine overhaul. Big diesel engines are harder on motor oil than any internal combustion engine. Do some research and fine out what kind of oil those big diesel engines are running. Synthetic was developed for gas turbine engines, not internal combustion engines. Most conventional motor oils have additives that include a synthetic component to improve thermal properties. They are cheaper than pure synth and provide adequate protection. Synthetic oils have been around for decades. If they were really as good as their manufacturers claim, why do you think that most automotive and motorcycle manufacturers use conventional oil from the factory? I know there are a lot of proponents of synthetic oil on this forum. I don't mean to start a war, but would recommend that you do your homework before deciding to make the shift to synthetic in an internal combustion engine. (END QUOTE) I guess "they" have moved on about flat spots on bearings, and engines not breaking in. And I never knew that diesel engines weren't internal combustion engines!
 
Messages
1,141
Location
Texas
"Every stroke of an internal combustion engine leaves a light film of oil in the combustion chamber. With dino oil, this film is combusted. With synthetic, because it has "such great thermal properties", the oil glazes to the combustion chamber and forms a ridge over time. This ridge will reduce the combustion area in effect raising compression. Over time, the compression can become to high resulting in combustion gases blowing by the piston and rings into the crankcase. The increased pressure will eventually take its toll on the connecting rods, bearings, and crank resulting in premature engine failure and more frequent engine overhaul." Could this be a possibility?
 
Messages
135
Location
Ramsey
quote:
Originally posted by JavaMan: the oil glazes to the combustion chamber and forms a ridge over time. This ridge will reduce the combustion area in effect raising compression.
No. There is not a build-up on the top of the cylinder. About 3/8 of an inch below the top of the cylinder is wore away from the rings contacting the wall of the cylinder. The reason the ware is more at the top of the cylinder is because the ignition of the combustion gas pressure is higher when the piston is at the top. The pressure not only pushes the rings down but it also pushes the rings out against the side of the cylinder wall. The ridge is there because cylinder wall material is worn away, not from build-up.
 
Messages
1,268
Location
SoCal, CA USA
Not only that, but when the piston goes from moving up to down, the ring will slightly deform, and quite possibly the edges of the rings will change angle (for lack of a better description) and those edges will rub the liner there. If you've ever looked at an old cylinder bore, the ridge is scraped into the wall, not a buildup. Scott
 
Messages
1,141
Location
Texas
"About 3/8 of an inch below the top of the cylinder is wore away from the rings contacting the wall of the cylinder." If this is the ridge/glaze that is being referred to I understand. There will be no wear above this point because there is no friction to erode the surface.
 
Messages
1,141
Location
Texas
I'm confused by the way you use the term "glaze". I was referring only to this statement: "Burn well? you ask. Every stroke of an internal combustion engine leaves a light film of oil in the combustion chamber. With dino oil, this film is combusted. With synthetic, because it has "such great thermal properties", the oil glazes to the combustion chamber and forms a ridge over time." I can't explain this any further.
 
Messages
135
Location
Ramsey
quote:
Originally posted by JavaMan: the oil glazes to the combustion chamber and forms a ridge over time."
Yeah, the statement that guy made is not correct. I think he makes people dumber by talking to them.
 
Messages
267
Location
Idaho
Every cylinder that I have ever measured showed zero wear at the ridge. And also zero buildup. That's a new one on me, never heard of anything that would actually add material to a cylinder wall while running, although JC Whitney used to sell those little miracle pellets that were purported to do this. Reckon maybe they were made of synthetic oil? Heavy equipment mechanics tell me that engines that are run long periods of time with fewer start/stop cycles will show a more even wear pattern top-to-bottom than typical auto engines, which usually show heavy wear just under the ridge and taper to almost no wear at the bottom. Joe
 
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