AndyH
Well-known member
Split from here:
http://www.mynissanleaf.com/viewtopic.php?p=57108#p57108
All else being the same, modifying engine oil to move from a 5000 mile oil change interval (OCI) to a 10,000 mile OCI requires that the base oil stay together for the duration. Then the oil needs more effective detergents to fight contaminants from both combustion and oil/additive break down. The oil needs more dispersant additives to keep cleaned contaminants in suspension and to keep them from agglomerating into...clumps...larger than bearing clearances and other passages. The oil needs more or stronger anti-oxidants and acid neutralizers. The oil needs more of the anti-wear additives that provide a sacrificial plating to fight metal to metal contact. While man-made synthetics generally don't use them, Group I, II, and III-based petroleum oils often require viscosity improver (VI) polymers to maintain the multi-grade temperature performance. The VI additives are usually the first components to be either chemically or physically broken down...and become the second or third targets for the detergent/dispersant additives after the old anti-wear package is cleaned and combustion byproducts are controlled.
Here's an example from three virgin oil analysis reports. These are 0W-20 oils on the market primarily for the Prius and other hybrids. There are a couple of different chemical compounds used as detergents, dispersants, and antiwear additives and they tend to be multi-function products. Looking at calcium, phosphorus, zinc, boron, and molybdenum will give us insight into those functions. Total base number gives us info on how long the oil can fight acid. Numbers are parts per million.
Oil 1: OEM 0W-20 (1 year or 10,000 mile OCI) (Group III)
Calcium: 1733
Phosphorus: 638
Zinc: 784
Boron: 200
Molybdenum: 1055
TBN: 6.53
Oil 2: Commercial 0W-20 (1 year or 10,000 mile OCI) (Group III/IV/V)
Calcium: 2599
Phosphorus: 733
Zinc: 879
Boron: 99
Molybdenum: 126
TBN: 8.45
Oil 3: Commercial 0W-20 (1 year or 25,000 mile OCI) (Group IV/V)
Calcium: 3376
Phosphorus: 737
Zinc: 892
Boron: 17
Molybdenum: 6
TBN: 10.10
[- Note the increasing level of calcium as the product's intended OCI increases - calcium is a primary component of the additive package's detergent.
- The moly in the first oil is likely a friction modifier. It works by plating on the engine's metal surfaces. It's activated by heat and pressure as are other extreme pressure additives. There must be metal to metal contact to provide the heat to activate the moly - one indicator that wear will increase until the moly is plated. One side effect of using moly is that it competes with the oil's anti-wear package, and its anti-rust/corrosion additives. The heavy use of moly also indicates that the oil is not a PAO/ester product as those bases have more than enough natural friction reducing properties - they generally don't need modifiers.
- Phosphorus and zinc are the prime components of ZDDP - a multi-function anti-wear, detergent, dispersant additive. Man-made synthetic oil has natural detergent properties in the PAO base oil and natural dispersant properties in the ester base oil component, so it doesn't need as strong an additive package to keep the engine clean. That's one reason why the third oil has more reserve detergent/dispersant capability than oil two even with similar levels of phosphorus and zinc.]
One other factor for oil change interval is oil and additive volatility. Most US oils, designed for much shorter drain intervals, and made primarily from petroleum, have lighter elements in the base oil that 'evaporate' off. Components from the additive package can volatilize as well. Not only to the vaporized elements tend to disrupt oxygen sensors, but the oil left behind is 'thicker' and consists of a higher number of longer-chain molecules. This thickened oil cannot lubricate as well. Man-made synthetic oil doesn't have the variable-length hydrocarbons in the base oil so there are significantly fewer lighter elements to boil off. The lower volatility means the oil stays in grade much longer and keeps the additives in the crankcase where they belong better than petroleum or petro-derived Group III 'synthetic'.
Here's a partial 'why'. The HVI product in the first diagram is Group III (highly processed petroleum) base oil.
source: "Synthetic Lubricants and High-Performance Functional Fluids", 2nd edition, page 14
The man-made polyalphaolefin is tailor-made and doesn't have contaminants or non-essential hydrocarbon elements. There are no 'lighter elements' to volatilize and no 'heavier elements' to remain as a higher viscosity byproduct.
Back to your car and your OCI. I'm not surprised that your 8K OCI works for you considering the oil that you use and the likelihood that it contains some Group III. Exxon-Mobil has been reducing the PAO/ester content of their oil in favor of less expensive Group III for years - that's the meaning of their "tri-synthetic" and super syn advertising. Group III base stock is more variable in composition and performance as its performance changes depending on the base oil used. Your OCI sweet spot would very likely improve if you used a Euro synthetic product (which by law must be man-made) or one of the US boutique products that is Group IV/V based (provided one carried the proper LL-xx performance rating).
http://www.mynissanleaf.com/viewtopic.php?p=57108#p57108
AndyH said:
I'll dig thru my library and get back with you on a reference. In the mean time, enjoy this article. After reading the info on how the anti-wear additives are removed/replated after new oil is introduced into the system, I did a couple of oil changes in my VW and did a series of oil samples at 500 mile intervals - and the rate of wear increased in the early portion of the new interval and was highest between 2000 and 3000 miles. The rate of wear dropped, stabilized, and remained in a zone until the oil started breaking down at end of life. In addition, as you might have read in the linked article), oil volatility is a factor - the lighter elements in the base oil and additive package tend to volatilize early in the oil change interval and this leads to contamination of oxygen sensors and exhaust aftertreatment devices (catalytic converters, etc.). (a 100% man-made synthetic has much lower volatility. The US 'synthetics' with at least some Group III have higher volatility. More below.)mogur said:
I guess my Euro generalization was a bit too broad - thanks. My desire for the post was to instill confidence in the system as long as one uses the proper oil quality. Regardless of pan sensor or not - the computer model is built from thousands of sets of oil analysis results from a wide range of driving.mogur said:
Why do you suggest that about 170K is 'high mileage' for a Euro car? As I've said, my VW in the driveway has 370K and change - on the original engine and turbo.mogur said:
I don't know the OEM BMW specs as well as I know the general ACEA sequences and OEM VWAG specs. It appears that BMW updates their specs on a three-year cycle - BMW LL-98, BMW LL-01, BMW LL-04, etc.mogur said:
Removing lead helped but caused other problems that it took a combination of fuel changes, lube oil changes, and engine design changes to overcome. Regardless of lead, we're still burning a hydrocarbon fuel in an oxygen/nitrogen environment and still generating a host of contaminants and acids.mogur said:
All else being the same, modifying engine oil to move from a 5000 mile oil change interval (OCI) to a 10,000 mile OCI requires that the base oil stay together for the duration. Then the oil needs more effective detergents to fight contaminants from both combustion and oil/additive break down. The oil needs more dispersant additives to keep cleaned contaminants in suspension and to keep them from agglomerating into...clumps...larger than bearing clearances and other passages. The oil needs more or stronger anti-oxidants and acid neutralizers. The oil needs more of the anti-wear additives that provide a sacrificial plating to fight metal to metal contact. While man-made synthetics generally don't use them, Group I, II, and III-based petroleum oils often require viscosity improver (VI) polymers to maintain the multi-grade temperature performance. The VI additives are usually the first components to be either chemically or physically broken down...and become the second or third targets for the detergent/dispersant additives after the old anti-wear package is cleaned and combustion byproducts are controlled.
Here's an example from three virgin oil analysis reports. These are 0W-20 oils on the market primarily for the Prius and other hybrids. There are a couple of different chemical compounds used as detergents, dispersants, and antiwear additives and they tend to be multi-function products. Looking at calcium, phosphorus, zinc, boron, and molybdenum will give us insight into those functions. Total base number gives us info on how long the oil can fight acid. Numbers are parts per million.
Oil 1: OEM 0W-20 (1 year or 10,000 mile OCI) (Group III)
Calcium: 1733
Phosphorus: 638
Zinc: 784
Boron: 200
Molybdenum: 1055
TBN: 6.53
Oil 2: Commercial 0W-20 (1 year or 10,000 mile OCI) (Group III/IV/V)
Calcium: 2599
Phosphorus: 733
Zinc: 879
Boron: 99
Molybdenum: 126
TBN: 8.45
Oil 3: Commercial 0W-20 (1 year or 25,000 mile OCI) (Group IV/V)
Calcium: 3376
Phosphorus: 737
Zinc: 892
Boron: 17
Molybdenum: 6
TBN: 10.10
[- Note the increasing level of calcium as the product's intended OCI increases - calcium is a primary component of the additive package's detergent.
- The moly in the first oil is likely a friction modifier. It works by plating on the engine's metal surfaces. It's activated by heat and pressure as are other extreme pressure additives. There must be metal to metal contact to provide the heat to activate the moly - one indicator that wear will increase until the moly is plated. One side effect of using moly is that it competes with the oil's anti-wear package, and its anti-rust/corrosion additives. The heavy use of moly also indicates that the oil is not a PAO/ester product as those bases have more than enough natural friction reducing properties - they generally don't need modifiers.
- Phosphorus and zinc are the prime components of ZDDP - a multi-function anti-wear, detergent, dispersant additive. Man-made synthetic oil has natural detergent properties in the PAO base oil and natural dispersant properties in the ester base oil component, so it doesn't need as strong an additive package to keep the engine clean. That's one reason why the third oil has more reserve detergent/dispersant capability than oil two even with similar levels of phosphorus and zinc.]
One other factor for oil change interval is oil and additive volatility. Most US oils, designed for much shorter drain intervals, and made primarily from petroleum, have lighter elements in the base oil that 'evaporate' off. Components from the additive package can volatilize as well. Not only to the vaporized elements tend to disrupt oxygen sensors, but the oil left behind is 'thicker' and consists of a higher number of longer-chain molecules. This thickened oil cannot lubricate as well. Man-made synthetic oil doesn't have the variable-length hydrocarbons in the base oil so there are significantly fewer lighter elements to boil off. The lower volatility means the oil stays in grade much longer and keeps the additives in the crankcase where they belong better than petroleum or petro-derived Group III 'synthetic'.
Here's a partial 'why'. The HVI product in the first diagram is Group III (highly processed petroleum) base oil.
source: "Synthetic Lubricants and High-Performance Functional Fluids", 2nd edition, page 14
The man-made polyalphaolefin is tailor-made and doesn't have contaminants or non-essential hydrocarbon elements. There are no 'lighter elements' to volatilize and no 'heavier elements' to remain as a higher viscosity byproduct.
Back to your car and your OCI. I'm not surprised that your 8K OCI works for you considering the oil that you use and the likelihood that it contains some Group III. Exxon-Mobil has been reducing the PAO/ester content of their oil in favor of less expensive Group III for years - that's the meaning of their "tri-synthetic" and super syn advertising. Group III base stock is more variable in composition and performance as its performance changes depending on the base oil used. Your OCI sweet spot would very likely improve if you used a Euro synthetic product (which by law must be man-made) or one of the US boutique products that is Group IV/V based (provided one carried the proper LL-xx performance rating).
