Is it really true that HDEOs have small amounts of friction modifiers, while passenger car oils have lots of it? If true, why is this so? Don't diesel engines have need for the stuff too?
Last edited:
Not much friction modifiers in HDEOs?
- Thread starter berniedd
- Start date
- Status
Fuel economy. PCMO's need more of them to increase the mileage of the cars they go into.
Also, gas engines rev much, much higher than diesel engines, so FM's are needed to protect the engine from this wear as well.
Some HDEO's do have substancial amounts of FM's - look at Schaeffer oils - over 300ppm of moly in their formulation. Delvac and Valvoline HDEO's also have moly in them.
Also, gas engines rev much, much higher than diesel engines, so FM's are needed to protect the engine from this wear as well.
Some HDEO's do have substancial amounts of FM's - look at Schaeffer oils - over 300ppm of moly in their formulation. Delvac and Valvoline HDEO's also have moly in them.
Highly friction modified oils are not so desirable in some applications, the one known the best here is the example of motorcycles that share a wet sump with the transmission. Less well cited is the effect in some heavy duty diesel engines where roller followers are used in contact with the cam though I have referenced one paper here a couple of times. Here is some further research.
From http://www.valvoline-technology.com/upload/dynamic/Diesel Engine Cam Galling.pdf
Quote:
ABSTRACT
Heavy Duty diesel engines typically use roller followers in
contact with the cam to reduce friction and
accommodate high Hertzian stresses. When the rolling
contact slips into sliding, cam galling can occur that may
lead to major cam failures. Oil traction has been
identified as a possible source to cause slipping. In this
study, oil traction was first measured in a Mini Traction
Machine (MTM). The results were then validated by a
series of engine tests to show that the measured oil
traction correlated with the occurrence of cam galling.
Finally, the MTM was used to evaluate various engine oil
formulations. It is concluded that some advanced base
oils, if not properly compensated by the additive
package, exhibit dangerously low oil traction. Oil traction
needs to be part of the oil formulation considerations.
The Scheaffer's guys should have something to say about the next one:
From: http://www.lnengineering.com/oil.html
Quote:
On the flip side, some advertise their product does not have moly intentionally, claiming moly is an abrasive and deposit forming, which are both true in as much as ZDDP, although forming good anti-wear films, it increases friction and the oil's traction coefficient. CMW Oil is one of the most vocal proponents of the elimination of moly all together from motor oils and does not use any moly friction modifiers in its street, race, or fleet lubricants. CMW is not alone in their recommendation against the use of moly in oils, with Cummins Engine Oil Recommendations, Bulletin No. 3810340-02, stating that "there is firm evidence that certain friction modifiers, molybdenum dithiophosphate for example, can in certain formulations result in cam follower pin failure at relatively low mileage." Also, molybdenum compounds in motor oils can degrade and cause bearing corrosion and is particularly aggressive towards copper. In almost all cases, any engine oil formula having "moly" will also contain a copper deactivator which will protect bearings from the moly compounds. The only problem, the copper deactivator decomposes at relatively low temperatures and looses it's potency after a few thousand miles, which can be seen in used oil analyses of moly rich oils having higher than normal copper levels. Link
Basically your question seems simple but seems to open a can of worms when you get into the literature. One solution to the aforementioned problems is a chane in materials in the roller-cam-pin inerface.
http://www.patentstorm.us/patents/6210503/description.html
US Patent 6210503 - Roller pin materials for enhanced cam durability , Cummins Engine Company
Quote:
During engine operation the roller element of the drive train rolling cam follower is continuously contacted by a rotating cam mounted on the camshaft. As a result, the roller rotates constantly when the engine is in operation. Most cam follower rollers are rotatably mounted in a cam follower assembly on a pin. The roller is typically made of steel, the cam follower assembly supporting lever is cast iron, and the pin securing the roller to the lever is bronze. The stresses produced on the cam follower assembly elements, particularly those at the interface between the cam follower roller and the pin, can cause, among other things, undesirable wear of the pin and adversely affect the rotational stability of the roller. Optimal camshaft cam and roller interface conditions cannot be maintained unless the roller is allowed to rotate freely. Without this freedom of rotation, such interface conditions as the maintenance of a lubricant film, the load distribution and the rolling contact may suffer significantly. The susceptibility of the roller pin to wear thus ultimately reduces cam life and engine efficiency because a valve or injector train with a worn pin cannot effectively support a roller to drive a valve or injector to operate with the timing accuracy required.
In addition to the timing problems that accompany worn roller pins, engines that utilize rolling cam followers experience reduced service life from damage to other valve or injector train components when the engine is shut off and started frequently. This reduction in service life results from damage to the camshaft cams and roller followers, primarily from material transfer, known as galling or scuffing, between the surfaces of the camshaft cams and the oscillating follower roller. If left unchecked, such galling eventually leads to spalling of the cam and the functional failure of the engine. High demand traction forces between the cam lobe and roller produces cam galling or scuffing. In extreme cases "skidding" of the roller may result, although damage to the cam may occur without skidding. This condition is particularly severe on startup and shutdown of the engine due to several factors, most of which are related to insufficient oil at the roller-pin interface. The low rotation speeds, characterized by an absence of hydrodynamic oil film, create high friction between the roller and the roller support pin. The insufficient oil supply at the pin-roller interface produces, at best, only a thin oil film, and wear of the pin material under this condition eventually leads to a more conformal contact with the roller, which further reduces the oil film thickness. Reducing the wear between the pin and roller during engine startup and shutdown would obviate these problems.
From http://www.valvoline-technology.com/upload/dynamic/Diesel Engine Cam Galling.pdf
Quote:
ABSTRACT
Heavy Duty diesel engines typically use roller followers in
contact with the cam to reduce friction and
accommodate high Hertzian stresses. When the rolling
contact slips into sliding, cam galling can occur that may
lead to major cam failures. Oil traction has been
identified as a possible source to cause slipping. In this
study, oil traction was first measured in a Mini Traction
Machine (MTM). The results were then validated by a
series of engine tests to show that the measured oil
traction correlated with the occurrence of cam galling.
Finally, the MTM was used to evaluate various engine oil
formulations. It is concluded that some advanced base
oils, if not properly compensated by the additive
package, exhibit dangerously low oil traction. Oil traction
needs to be part of the oil formulation considerations.
The Scheaffer's guys should have something to say about the next one:
From: http://www.lnengineering.com/oil.html
Quote:
On the flip side, some advertise their product does not have moly intentionally, claiming moly is an abrasive and deposit forming, which are both true in as much as ZDDP, although forming good anti-wear films, it increases friction and the oil's traction coefficient. CMW Oil is one of the most vocal proponents of the elimination of moly all together from motor oils and does not use any moly friction modifiers in its street, race, or fleet lubricants. CMW is not alone in their recommendation against the use of moly in oils, with Cummins Engine Oil Recommendations, Bulletin No. 3810340-02, stating that "there is firm evidence that certain friction modifiers, molybdenum dithiophosphate for example, can in certain formulations result in cam follower pin failure at relatively low mileage." Also, molybdenum compounds in motor oils can degrade and cause bearing corrosion and is particularly aggressive towards copper. In almost all cases, any engine oil formula having "moly" will also contain a copper deactivator which will protect bearings from the moly compounds. The only problem, the copper deactivator decomposes at relatively low temperatures and looses it's potency after a few thousand miles, which can be seen in used oil analyses of moly rich oils having higher than normal copper levels. Link
Basically your question seems simple but seems to open a can of worms when you get into the literature. One solution to the aforementioned problems is a chane in materials in the roller-cam-pin inerface.
http://www.patentstorm.us/patents/6210503/description.html
US Patent 6210503 - Roller pin materials for enhanced cam durability , Cummins Engine Company
Quote:
During engine operation the roller element of the drive train rolling cam follower is continuously contacted by a rotating cam mounted on the camshaft. As a result, the roller rotates constantly when the engine is in operation. Most cam follower rollers are rotatably mounted in a cam follower assembly on a pin. The roller is typically made of steel, the cam follower assembly supporting lever is cast iron, and the pin securing the roller to the lever is bronze. The stresses produced on the cam follower assembly elements, particularly those at the interface between the cam follower roller and the pin, can cause, among other things, undesirable wear of the pin and adversely affect the rotational stability of the roller. Optimal camshaft cam and roller interface conditions cannot be maintained unless the roller is allowed to rotate freely. Without this freedom of rotation, such interface conditions as the maintenance of a lubricant film, the load distribution and the rolling contact may suffer significantly. The susceptibility of the roller pin to wear thus ultimately reduces cam life and engine efficiency because a valve or injector train with a worn pin cannot effectively support a roller to drive a valve or injector to operate with the timing accuracy required.
In addition to the timing problems that accompany worn roller pins, engines that utilize rolling cam followers experience reduced service life from damage to other valve or injector train components when the engine is shut off and started frequently. This reduction in service life results from damage to the camshaft cams and roller followers, primarily from material transfer, known as galling or scuffing, between the surfaces of the camshaft cams and the oscillating follower roller. If left unchecked, such galling eventually leads to spalling of the cam and the functional failure of the engine. High demand traction forces between the cam lobe and roller produces cam galling or scuffing. In extreme cases "skidding" of the roller may result, although damage to the cam may occur without skidding. This condition is particularly severe on startup and shutdown of the engine due to several factors, most of which are related to insufficient oil at the roller-pin interface. The low rotation speeds, characterized by an absence of hydrodynamic oil film, create high friction between the roller and the roller support pin. The insufficient oil supply at the pin-roller interface produces, at best, only a thin oil film, and wear of the pin material under this condition eventually leads to a more conformal contact with the roller, which further reduces the oil film thickness. Reducing the wear between the pin and roller during engine startup and shutdown would obviate these problems.
MolaKule
Staff member
Quote:
Cummins Engine Oil Recommendations, Bulletin No. 3810340-02, stating that "there is firm evidence that certain friction modifiers, molybdenum dithiophosphate for example, can in certain formulations result in cam follower pin failure at relatively low mileage.
This is very old info.
Let's clarify again so as not to perpetuate misinformation, that HDEO's and PCMO's do NOT use molybdenum dithiophosphate, but use Molybdenum DTC's or dithiocarbamates, which do not cause bearing corrosion. In addition, metal deactivators, which are present in HDEO's, are there to resist any metal attack.
MoDTP is used in hydraulic oils with no problems.
Cummins Engine Oil Recommendations, Bulletin No. 3810340-02, stating that "there is firm evidence that certain friction modifiers, molybdenum dithiophosphate for example, can in certain formulations result in cam follower pin failure at relatively low mileage.
This is very old info.
Let's clarify again so as not to perpetuate misinformation, that HDEO's and PCMO's do NOT use molybdenum dithiophosphate, but use Molybdenum DTC's or dithiocarbamates, which do not cause bearing corrosion. In addition, metal deactivators, which are present in HDEO's, are there to resist any metal attack.
MoDTP is used in hydraulic oils with no problems.
MolaKule
Staff member
http://www.bobistheoilguy.com/forums/ubbthreads.php?ubb=showflat&Number=530321#Post530321
#530330
There are other purely organic friction modifiers and since moly is getting expensive, I see a shift to purely non-metallic DTC's.
#530330
There are other purely organic friction modifiers and since moly is getting expensive, I see a shift to purely non-metallic DTC's.
Last edited:
How then are syn oils as claimed by some to be more slippery?
MolaKule
Staff member
First of all, the term "slippery" is not a term that is quantifiable. I think "lubricity" is the term used often but it is not a good term to use either.
Unadditized synthetic base oils, especially esters, have a lower friction coefficient than do Mineral oils.
Add fatty acids, specialized esters (other than ester base oils) and other FM compounds, and the friction coefficient drops even further.
Remember, there is a difference between friction reducers and anti-wear agents.
Unadditized synthetic base oils, especially esters, have a lower friction coefficient than do Mineral oils.
Add fatty acids, specialized esters (other than ester base oils) and other FM compounds, and the friction coefficient drops even further.
Remember, there is a difference between friction reducers and anti-wear agents.
Last edited:
Originally Posted By: jmac
. Less well cited is the effect in some heavy duty diesel engines where roller followers are used in contact with the cam though I have referenced one paper here a couple of times.
What I don't understand is why this is (apparently?) never seen in gasoline engines, which started using roller cam followers back in the mid 80s.
. Less well cited is the effect in some heavy duty diesel engines where roller followers are used in contact with the cam though I have referenced one paper here a couple of times.
What I don't understand is why this is (apparently?) never seen in gasoline engines, which started using roller cam followers back in the mid 80s.
- Status
Similar threads
