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Ive posted this as there have been the occasional question on oil. These are my views only based on a considerable amount of reading on the net (Im not an engineer or chemist). The great oil debate (as it is dubbed) has deforrested whole continents on the Harley forums where it is talked about endlessly and being the lonely person I am I actually read.
These are only my views. So do not take any notice of them. Im not qualified in the appropriate field, they have not been peer reviewed, I have probably misunderstood what I read which was probably written by people as misinformed as me.
I have not intended to show a lack of respect to any one by issuing this thread. If you disagree with what I have written feel free to explain but please no flaming.
The only thing I can say unequivically about oils is follow the manufacturers recommendations (type, viscosity, change intervals) and you cant go wrong.
I will probably add to this occasionally.
Synthetic for Bedding In.- should not be used for bedding in an engine (even though may be OK for some). It does not allow proper bedding in of parts. Even the oil co tech people dont fully undersatnd why. Their recommendation is at least 6000km (or was it 10 - Ill check) on Dino before going synth.
Cushioning Affect of Higher Viscosity Oils - My understanding is the "Cushioning effect" is created mainly by the oil pressure not the viscosity (which has minor impact). W50 oils are specified for older engines where manufacturing tolerances were much higher. In a modern engine there is no benefit in going heavier than the viscosity specified for your operating environment. Ie if your manual says w40 then no benefit of using w50 - it may actually increase wear as the oil passages may be narrow so thicker oil will not flow as fast.
As a test on the cushioning affect - if w50 gives better protection and less wear than w40 due to its thickness then w70 must be better still - imagine - no wear at all!!
In old and worn engines "thick" oil may have a cushioning affect (because the tolerances are now so large through wear) but the main reason for its use seems to be to stop smoking by "sealing" the piston rings etc.
A couple of things about viscosity. Use the lowest cold weight you can (see proviso below) so that the oil circulates quicker on starting when most engine wear occurs. Even 0 cold weight is thicker when cold than hot W40.
BTW - blipping the throttle immedialtey on start up probably increases wear because you increase the revolutions before the oil has had enough time to circulate to all the bearing / journals, the top end (especially) etc at the right pressure. This is supposed to be minimised in some oils that leave a lubricating coating on the metal parts (ie Intellegent molecules of Castrol Magnatec). However if you remember that at idle your engine has turned over 20 times in the first second the protective properties is probably pretty limited so dont blip until the oil has fully circulated (in some cars engines it will take several seconds before the oil pressure is high enough to turn off the warning light).
Viscosity Loss - all oils lose viscosity and the greater the viscosity "range" the more likely to lose "weight" ie for example a 10W40 will "degrade" faster than a 20w40 (all else being equal). This is one of the many resons why maintaing regualar oil changes is necessary and it is one of the important characteristics measured if you use oil analysis to determine when you should change oils. For this reason it is probably unwise to use a 0w30 oil although I note one of the tech guys / mechanics on the Porche forum recommends using 0wXX weight. However a m/c magazine that tested oil found the "racing oils ie 0w30 didn't keep their viscosity.
Viscosity Loss and Synth - One of the advantages of Synthetic oil is that because it is "man made" and has a more consistent molecular structure it does not need as much VI (viscosity improvers) as Dino oil so stays in grade longer ( one test Synth lost 7% viscosity and Dino 14% or thereabouts). However there is a very wide range within oils of the same weighting.
M/C versus Car Oils - more later.
These are only my views. So do not take any notice of them. Im not qualified in the appropriate field, they have not been peer reviewed, I have probably misunderstood what I read which was probably written by people as misinformed as me.
I have not intended to show a lack of respect to any one by issuing this thread. If you disagree with what I have written feel free to explain but please no flaming.
The only thing I can say unequivically about oils is follow the manufacturers recommendations (type, viscosity, change intervals) and you cant go wrong.
I will probably add to this occasionally.
Synthetic for Bedding In.- should not be used for bedding in an engine (even though may be OK for some). It does not allow proper bedding in of parts. Even the oil co tech people dont fully undersatnd why. Their recommendation is at least 6000km (or was it 10 - Ill check) on Dino before going synth.
Cushioning Affect of Higher Viscosity Oils - My understanding is the "Cushioning effect" is created mainly by the oil pressure not the viscosity (which has minor impact). W50 oils are specified for older engines where manufacturing tolerances were much higher. In a modern engine there is no benefit in going heavier than the viscosity specified for your operating environment. Ie if your manual says w40 then no benefit of using w50 - it may actually increase wear as the oil passages may be narrow so thicker oil will not flow as fast.
As a test on the cushioning affect - if w50 gives better protection and less wear than w40 due to its thickness then w70 must be better still - imagine - no wear at all!!
In old and worn engines "thick" oil may have a cushioning affect (because the tolerances are now so large through wear) but the main reason for its use seems to be to stop smoking by "sealing" the piston rings etc.
A couple of things about viscosity. Use the lowest cold weight you can (see proviso below) so that the oil circulates quicker on starting when most engine wear occurs. Even 0 cold weight is thicker when cold than hot W40.
BTW - blipping the throttle immedialtey on start up probably increases wear because you increase the revolutions before the oil has had enough time to circulate to all the bearing / journals, the top end (especially) etc at the right pressure. This is supposed to be minimised in some oils that leave a lubricating coating on the metal parts (ie Intellegent molecules of Castrol Magnatec). However if you remember that at idle your engine has turned over 20 times in the first second the protective properties is probably pretty limited so dont blip until the oil has fully circulated (in some cars engines it will take several seconds before the oil pressure is high enough to turn off the warning light).
Viscosity Loss - all oils lose viscosity and the greater the viscosity "range" the more likely to lose "weight" ie for example a 10W40 will "degrade" faster than a 20w40 (all else being equal). This is one of the many resons why maintaing regualar oil changes is necessary and it is one of the important characteristics measured if you use oil analysis to determine when you should change oils. For this reason it is probably unwise to use a 0w30 oil although I note one of the tech guys / mechanics on the Porche forum recommends using 0wXX weight. However a m/c magazine that tested oil found the "racing oils ie 0w30 didn't keep their viscosity.
Viscosity Loss and Synth - One of the advantages of Synthetic oil is that because it is "man made" and has a more consistent molecular structure it does not need as much VI (viscosity improvers) as Dino oil so stays in grade longer ( one test Synth lost 7% viscosity and Dino 14% or thereabouts). However there is a very wide range within oils of the same weighting.
M/C versus Car Oils - more later.