GT4
Well-known member
- Joined
- 8 Nov 2008
- Messages
- 30,181
[EDITED AS BAZ DOESN'T LIKE THE TITLE - HE IS CONFUSED BY CAUSE AND EFFECT]
I have been asked if it is better for a M96 or M97 engines (that's the standard 986,996,987.1 and 997.1 blocks) to run high viscosity oils, like 10w40.
And the short answer is no.
The reason is the favourite bête noir of the water-cooled flat sixes - the IMS (intermediate shaft).
Excluding the new Gen 2 MA.01 and MA.02 DFI engines, which cleverly circumvent this issue by not having an IMS!
The M96/M97 are VERY oil hungry, but only thin oil hungry.
The oil not only lubricates and cools as in any engine, but it also runs some very important systems:
Low oil levels and low oil pressure (at idle when the engine is hot) can result in some or all systems inside the engine being starved of oil.
Lack of oil to these systems (which control the valves etc) will at best cause increased component wear and reduced operating life, at worth their destruction and ensuing catastrophic engine failure.
It is the oil pump at the end of the IMS that puts the biggest rotational stress on the IMS. However, ironically, it is the oil pump that actuates the Variocam system that needs to be supplied with equal, stable and sufficient oil and oil pressures to prevent IMS imbalances (lateral stress) and bearing stresses!
Ignore all the numerous IMS and IMS bearing and IMS seal modifications that Porsche made over the years (three just during the 996's lifetime, two more in the 997's lifetime, not including its final removal).
None of these fixed the problem: they were attempting to cure for IMS stresses, not a prevention of them.
The THREE most probable reasons that could cause IMS failure are:
1) Manufacturing fractures to bearing/bearing cage or shaft - this is "discovered" quite quickly during the engines life and is almost instant in its failure mode. Usually only affects one batch of bearings or shafts. IMS failures have spanned a DECADE. This is not likely to represent a common cause over time. Under German and US laws Porsche would have to document the issue to the relevant TuV/DoT regulators. No such documents have been filed.
2) Out of balance shaft due to manufacturing or build alignment - this would cause the bearings to rapidly wear, wear unevenly and eventually collapse. However, the noise created by an out of balance IMS would be unmistakably evident on start up. The engine would run badly as the valve timing would-be out and would trigger the DME to illuminate the CEL (engine warning) to full emergency FLASH mode (warning of impending disaster). This would allow an observant driver enough time to turn off the engine before it explodes. Again, if this were to occur, once the engine had been returned to Porsche and investigated, under German and US laws Porsche would have to document the issue to the relevant TuV/DoT regulators. No such documents have been filed.
3) Lack of engine oil to hydraulic systems - this is caused by both true low oil, the wrong oil and instantaneous low oil (starvation) during start-up, high hydraulic use and high-G cornering etc. This is the most likely cause of the intermediate bearing collapse. This is NOT to be confused with the oil (grease) in or not in the IMS ball-races, this is the hydraulic and general oil system the IMS pumps and uses to balance itself (or at least without, becomes imbalanced).
(3) has no other cause other than the owner or driver's use or abuse.
Porsche partially recognised this oil significance and bumped up the 996 crankcase capacity by another 6% (0.5 litres) in MY1999 and also modified the bearing housing (this is in addition to the three 996 direct IMS mods).
So, the oil should always be filled to the brim (so to speak), we know that (and can handily check from the driver's seat without even pulling the dipstick, you have no excuse!).
But what oil?
Well Porsche is pretty specific and unequivocal about this: 0w40.
Yes, it is thin and, yes, that means it can leak (especially with an old or ill fitting RMS), but to not bother getting to the cause and rectifying seals and gaskets or simply tightening block bolts etc by bodging with a thicker (non-leaky) oil is inexcusable.
The "0w" in that code means it is exceptional thin when cold.
This is when the engine is at most stress, the pump is at most stress, the engine is unlubricated, all those hydraulic systems (tappets, Variocam, VariocamPlus etc) are all unpressurised and ineffective.
So help it out: the "0w" (low viscosity oil) will operate all its hydraulic systems as quickly as possible and get around the engine quicker and hence reduce your start-up wear.
Most importantly, when it comes to the IMS, the super thin "0w" will be less stress on the pump at the end of the shaft and will balance the Variocam tensioners across the IMS quicker, and hence reduce IMS bearing stress.
Because of all this, DON'T rag it cold either, or even "warm", wait until it is good and hot (at operating temp and oil pressure <2 bar at idle), then the oil is even thinner. That oil pressure gauge is saying how much stress the pump and IMS are under. Try to minimise it.
In the words of Swiss Tony:
"Driving a Porsche is like making love to a beautiful woman - make sure she's hot and wet before the rough stuff" (or something like that)
Here is the IMS and the oil pump, and the Variocam tensioners and the VariocamPlus cam control and the valves etc etc:
I have been asked if it is better for a M96 or M97 engines (that's the standard 986,996,987.1 and 997.1 blocks) to run high viscosity oils, like 10w40.
And the short answer is no.
The reason is the favourite bête noir of the water-cooled flat sixes - the IMS (intermediate shaft).
Excluding the new Gen 2 MA.01 and MA.02 DFI engines, which cleverly circumvent this issue by not having an IMS!
The M96/M97 are VERY oil hungry, but only thin oil hungry.
The oil not only lubricates and cools as in any engine, but it also runs some very important systems:
- Hydraulic tappets (for valve control from the cams)
Variocam (all models - eg 996 3.4/3.6) hydraulic chain tensioners (for valve timing control, must be in equilibrium to balance IMS)
VariocamPlus (later models - eg 996 3.6) hydraulic cam lobe actuation (for valve range control)
Low oil levels and low oil pressure (at idle when the engine is hot) can result in some or all systems inside the engine being starved of oil.
Lack of oil to these systems (which control the valves etc) will at best cause increased component wear and reduced operating life, at worth their destruction and ensuing catastrophic engine failure.
It is the oil pump at the end of the IMS that puts the biggest rotational stress on the IMS. However, ironically, it is the oil pump that actuates the Variocam system that needs to be supplied with equal, stable and sufficient oil and oil pressures to prevent IMS imbalances (lateral stress) and bearing stresses!
Ignore all the numerous IMS and IMS bearing and IMS seal modifications that Porsche made over the years (three just during the 996's lifetime, two more in the 997's lifetime, not including its final removal).
None of these fixed the problem: they were attempting to cure for IMS stresses, not a prevention of them.
The THREE most probable reasons that could cause IMS failure are:
1) Manufacturing fractures to bearing/bearing cage or shaft - this is "discovered" quite quickly during the engines life and is almost instant in its failure mode. Usually only affects one batch of bearings or shafts. IMS failures have spanned a DECADE. This is not likely to represent a common cause over time. Under German and US laws Porsche would have to document the issue to the relevant TuV/DoT regulators. No such documents have been filed.
2) Out of balance shaft due to manufacturing or build alignment - this would cause the bearings to rapidly wear, wear unevenly and eventually collapse. However, the noise created by an out of balance IMS would be unmistakably evident on start up. The engine would run badly as the valve timing would-be out and would trigger the DME to illuminate the CEL (engine warning) to full emergency FLASH mode (warning of impending disaster). This would allow an observant driver enough time to turn off the engine before it explodes. Again, if this were to occur, once the engine had been returned to Porsche and investigated, under German and US laws Porsche would have to document the issue to the relevant TuV/DoT regulators. No such documents have been filed.
3) Lack of engine oil to hydraulic systems - this is caused by both true low oil, the wrong oil and instantaneous low oil (starvation) during start-up, high hydraulic use and high-G cornering etc. This is the most likely cause of the intermediate bearing collapse. This is NOT to be confused with the oil (grease) in or not in the IMS ball-races, this is the hydraulic and general oil system the IMS pumps and uses to balance itself (or at least without, becomes imbalanced).
(3) has no other cause other than the owner or driver's use or abuse.
Porsche partially recognised this oil significance and bumped up the 996 crankcase capacity by another 6% (0.5 litres) in MY1999 and also modified the bearing housing (this is in addition to the three 996 direct IMS mods).
So, the oil should always be filled to the brim (so to speak), we know that (and can handily check from the driver's seat without even pulling the dipstick, you have no excuse!).
But what oil?
Well Porsche is pretty specific and unequivocal about this: 0w40.
Yes, it is thin and, yes, that means it can leak (especially with an old or ill fitting RMS), but to not bother getting to the cause and rectifying seals and gaskets or simply tightening block bolts etc by bodging with a thicker (non-leaky) oil is inexcusable.
The "0w" in that code means it is exceptional thin when cold.
This is when the engine is at most stress, the pump is at most stress, the engine is unlubricated, all those hydraulic systems (tappets, Variocam, VariocamPlus etc) are all unpressurised and ineffective.
So help it out: the "0w" (low viscosity oil) will operate all its hydraulic systems as quickly as possible and get around the engine quicker and hence reduce your start-up wear.
Most importantly, when it comes to the IMS, the super thin "0w" will be less stress on the pump at the end of the shaft and will balance the Variocam tensioners across the IMS quicker, and hence reduce IMS bearing stress.
Because of all this, DON'T rag it cold either, or even "warm", wait until it is good and hot (at operating temp and oil pressure <2 bar at idle), then the oil is even thinner. That oil pressure gauge is saying how much stress the pump and IMS are under. Try to minimise it.
In the words of Swiss Tony:
"Driving a Porsche is like making love to a beautiful woman - make sure she's hot and wet before the rough stuff" (or something like that)
Here is the IMS and the oil pump, and the Variocam tensioners and the VariocamPlus cam control and the valves etc etc: