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Message: I think you are making two erroneous assumptions
Changed By: grant
Change Date: October 26, 2014 11:39AM
I think you are making two erroneous assumptions
Change Date: October 26, 2014 11:39AM
I think you are making two erroneous assumptions
Before i go into it - your position is, of course, the "safer" position. It will always be fine - no risk. But i has a cost, about double for the oil.
And i think the risk is negligible. But if you want no risk, ....there is no such thing.
In truth they two assumptions/points are related....so maybe there is just one...
The first is that, at moderate temperatures, a 5w30 is thinner than a 5w40. While in practice it is, marginally, its really very small. It simply has a narrower range over which it maintains its film strength. Look at the ACEA or SAE curves, or the even better ones from Lubrizol.
The second is that the oil pressure at idle will be lower with a 5w30. It is certainly possible, depending on the oil, but its unlikely to be significant. again, they will have very similar viscosities in the range of 125-175 degF, which we are probably focused on. We're just flushing contaminated oil and putting around town a few miles, right?
Bear in mind that until very recently Porsche recommended 5w30 and 10w30 for "ambient typically below 50degF" They understand the temperature relationship.
I will almost promise that a 5w30 will have better film strength at 175degF than a 5w40 will at 250 degF.
I too have oil pressure and temp gauges in two cars. It shows zippo difference between them until quite hot. (not Porsche motors, but motors are motors)
Finally, the concern with thin oil is not that it will fail to float a bearing under most normal pressures, but that it cannot continue to do it when the pressure is high, combined with the rpms being high and the temperature being high, which is what the HT/HS test measures. Note that Porches A40 list is nearly a match of "search on A3/B4", which explicitly sacrifices other qualities for HT/HS.
In fact all this points to why i also suggest the flip side as well - only for hot/fast/hard use, that we intelligently modify Porsche's recommendations to maintain the viscosity and film strength under those circumstances. Its the flip side. For the record, when racing, Porsche does just this.
Grant
And i think the risk is negligible. But if you want no risk, ....there is no such thing.
In truth they two assumptions/points are related....so maybe there is just one...
The first is that, at moderate temperatures, a 5w30 is thinner than a 5w40. While in practice it is, marginally, its really very small. It simply has a narrower range over which it maintains its film strength. Look at the ACEA or SAE curves, or the even better ones from Lubrizol.
The second is that the oil pressure at idle will be lower with a 5w30. It is certainly possible, depending on the oil, but its unlikely to be significant. again, they will have very similar viscosities in the range of 125-175 degF, which we are probably focused on. We're just flushing contaminated oil and putting around town a few miles, right?
Bear in mind that until very recently Porsche recommended 5w30 and 10w30 for "ambient typically below 50degF" They understand the temperature relationship.
I will almost promise that a 5w30 will have better film strength at 175degF than a 5w40 will at 250 degF.
I too have oil pressure and temp gauges in two cars. It shows zippo difference between them until quite hot. (not Porsche motors, but motors are motors)
Finally, the concern with thin oil is not that it will fail to float a bearing under most normal pressures, but that it cannot continue to do it when the pressure is high, combined with the rpms being high and the temperature being high, which is what the HT/HS test measures. Note that Porches A40 list is nearly a match of "search on A3/B4", which explicitly sacrifices other qualities for HT/HS.
In fact all this points to why i also suggest the flip side as well - only for hot/fast/hard use, that we intelligently modify Porsche's recommendations to maintain the viscosity and film strength under those circumstances. Its the flip side. For the record, when racing, Porsche does just this.
Grant
Original Message
Author: grantDate: October 26, 2014 11:35AM
I think you are making two erroneous assumptions
In truth they are related....so maybe there is just one...
The first is that, at moderate temperatures, a 5w30 is thinner than a 5w40. While in practice it is, marginally, its really very small. It simply has a narrower range over which it maintains its film strength. Look at the ACEA or SAE curves, or the even better ones from Lubrizol.
The second is that the oil pressure at idle will be lower with a 5w30. It is certainly possible, depending on the oil, but its unlikely to be significant. again, they will have very similar viscosities in the range of 125-175 degF, which we are probably focused on. We're just flushing contaminated oil and putting around town a few miles, right?
Bear in mind that until very recently Porsche recommended 5w30 and 10w30 for "ambient typically below 50degF" They understand the temperature relationship.
I will almost promise that a 5w30 will have better film strength at 175degF than a 5w40 will at 250 degF.
I too have oil pressure and temp gauges in two cars. It shows zippo difference between them until quite hot. (not Porsche motors, but motors are motors)
Finally, the concern with thin oil is not that it will fail to float a bearing under most normal pressures, but that it cannot continue to do it when the pressure is high, combined with the rpms being high and the temperature being high, which is what the HT/HS test measures. Note that Porches A40 list is nearly a match of "search on A3/B4", which explicitly sacrifices other qualities for HT/HS.
In fact all this points to why i also suggest the flip side as well - only for hot/fast/hard use, that we intelligently modify Porsche's recommendations to maintain the viscosity and film strength under those circumstances. Its the flip side. For the record, when racing, Porsche does just this.
Grant
The first is that, at moderate temperatures, a 5w30 is thinner than a 5w40. While in practice it is, marginally, its really very small. It simply has a narrower range over which it maintains its film strength. Look at the ACEA or SAE curves, or the even better ones from Lubrizol.
The second is that the oil pressure at idle will be lower with a 5w30. It is certainly possible, depending on the oil, but its unlikely to be significant. again, they will have very similar viscosities in the range of 125-175 degF, which we are probably focused on. We're just flushing contaminated oil and putting around town a few miles, right?
Bear in mind that until very recently Porsche recommended 5w30 and 10w30 for "ambient typically below 50degF" They understand the temperature relationship.
I will almost promise that a 5w30 will have better film strength at 175degF than a 5w40 will at 250 degF.
I too have oil pressure and temp gauges in two cars. It shows zippo difference between them until quite hot. (not Porsche motors, but motors are motors)
Finally, the concern with thin oil is not that it will fail to float a bearing under most normal pressures, but that it cannot continue to do it when the pressure is high, combined with the rpms being high and the temperature being high, which is what the HT/HS test measures. Note that Porches A40 list is nearly a match of "search on A3/B4", which explicitly sacrifices other qualities for HT/HS.
In fact all this points to why i also suggest the flip side as well - only for hot/fast/hard use, that we intelligently modify Porsche's recommendations to maintain the viscosity and film strength under those circumstances. Its the flip side. For the record, when racing, Porsche does just this.
Grant