Motor oil aging, wear and consideration when to change it.
As I was thinking how to explain the aging and some important parameters of a motor oil, I came to two interesting links which I must post here.
The first is about measuring the reserve alkalinity which is important because it shows how much detergent the oil still is (1. blocks the formation of bigger carbon aggregates and 2. neutralizes any acidic compounds from combustion and burned oil itself) and you can see the rapidly increasing wear when they are depleted here.
The second is how to interpret the parameters of the oil. You can start reading at Oxidation, then following the AN/BN (acid number, base number) explanation. This helps to have in mind when comparing the BN (reserve alkalinity) in an oil, plus the Sulfated ash. There are some new oils which are low in ash, but still have high reserve alkalinity.
A worn engine would like to have oil with high BN number and still low in ash and good viscosity (not very low).
The reason behind this is: Since the blow-by sprays the oil into fine mist which is then burned by the engine - you need low ash oil. (all modern oils are low-ash, well the very new API-CJ is even half of that! :D)
You need high reserve alkalinity to neutralize all the trapped acidic gases that blow-by the piston rings, plus you need to wash and disperse increased amount of soot. Plus there is this burned oil mist that you partially need to wash too. (It can behave as a weak acid.)
More viscous oils are not that easy to spray, so the more viscosity an oil has at HIGH temperatures the less of the oil is likely to be sprayed into a fine mist. But the low temperature viscosity has to stay adequately LOW, because you still need to cool the oil and you need to start in a cold winter too.
The fourth thing to be taken into consideration is the price... a Fully syntetic diesel motor oil of viscosity SAE 20W-50 MB228.5 would be lovely, but the price is not!
More ideas maybe later.
for my Mercedes friends, more links.
Some site with Mercedes oil specs explanation.
some more later...
and finally, my private motor oil explanation, some table with available oils to me with pricing and explanation of what is what... English verion as time/donating permits.
SHPD, UHPD motor oils
The first is about measuring the reserve alkalinity which is important because it shows how much detergent the oil still is (1. blocks the formation of bigger carbon aggregates and 2. neutralizes any acidic compounds from combustion and burned oil itself) and you can see the rapidly increasing wear when they are depleted here.
The second is how to interpret the parameters of the oil. You can start reading at Oxidation, then following the AN/BN (acid number, base number) explanation. This helps to have in mind when comparing the BN (reserve alkalinity) in an oil, plus the Sulfated ash. There are some new oils which are low in ash, but still have high reserve alkalinity.
A worn engine would like to have oil with high BN number and still low in ash and good viscosity (not very low).
The reason behind this is: Since the blow-by sprays the oil into fine mist which is then burned by the engine - you need low ash oil. (all modern oils are low-ash, well the very new API-CJ is even half of that! :D)
You need high reserve alkalinity to neutralize all the trapped acidic gases that blow-by the piston rings, plus you need to wash and disperse increased amount of soot. Plus there is this burned oil mist that you partially need to wash too. (It can behave as a weak acid.)
More viscous oils are not that easy to spray, so the more viscosity an oil has at HIGH temperatures the less of the oil is likely to be sprayed into a fine mist. But the low temperature viscosity has to stay adequately LOW, because you still need to cool the oil and you need to start in a cold winter too.
The fourth thing to be taken into consideration is the price... a Fully syntetic diesel motor oil of viscosity SAE 20W-50 MB228.5 would be lovely, but the price is not!
More ideas maybe later.
for my Mercedes friends, more links.
Some site with Mercedes oil specs explanation.
some more later...
and finally, my private motor oil explanation, some table with available oils to me with pricing and explanation of what is what... English verion as time/donating permits.
SHPD, UHPD motor oils
posted by Mario. at 3:32 PM
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