How is "excessive" oil consumption measured?
10-08-2008, 11:51 AM
#16
Drifting
From a practical point of view there is a consumption level where emissions testing will fail, smoke will come out of the tail pipe, converters will plug, spark plugs will foul, detonation will occur, etc. What that consumption level is I am not sure but 1 quart/400 miles can't be too far off. I think I am at about 1 quart/3000 miles so I won't worry yet.
10-08-2008, 12:48 PM
#17
RL Technical Advisor
I certainly do,...
Naturally, the only way one can accurately assess oil consumption is to be consistent about measuring oil level and that means following the factory's procedures very carefully.
Having seen a whole slew of overfilled 911's in my time (a few with bent rods), it always stems from the person using the guage to determine oil level. IMHO, that instrument is simply a "red herring" and is largely responsible for the overfilled cars and ensuing mess that makes.
Accurate measurements of oil level is by using the dipstick and that device is only reliable when the engine is at full operating temperature after idling for 3 minutes on level ground. Admittedly, Porsche didn't make it easy to do on the 3.6 cars with that long dipstick tube but patience is rewarded with a little practice.
The guage is useful for confirming, not assessing, oil level and once again, after the hot engine has been idling for 3 minutes on level ground.
Naturally, the only way one can accurately assess oil consumption is to be consistent about measuring oil level and that means following the factory's procedures very carefully.
Having seen a whole slew of overfilled 911's in my time (a few with bent rods), it always stems from the person using the guage to determine oil level. IMHO, that instrument is simply a "red herring" and is largely responsible for the overfilled cars and ensuing mess that makes.
Accurate measurements of oil level is by using the dipstick and that device is only reliable when the engine is at full operating temperature after idling for 3 minutes on level ground. Admittedly, Porsche didn't make it easy to do on the 3.6 cars with that long dipstick tube but patience is rewarded with a little practice.
The guage is useful for confirming, not assessing, oil level and once again, after the hot engine has been idling for 3 minutes on level ground.
Last edited by Steve Weiner-Rennsport Systems; 10-08-2008 at 05:50 PM. Reason: Syntax correction
10-08-2008, 03:41 PM
#18
Rennlist Member
Just for fun, extending this discussion into the consquences of excessive oil implies that it enters the combustion chamber, where we assume that oil burns incompletely and fouls up things such as the SAI ports .... leading to PO410/411 codes ringing in: if true mechanical failings such as worn valve guides and/or worn rings contribute to this mechanism .... then the combustion chamber would react the same to oil introduced via aspiration from overfilling, n'est ce pas? Oil is oil, regardless of how it presents itself in front of a pair of sparkplugs ....
If there is a grain of reality to this, then overfilling can contribute to SAI issues on perfectly healthy engines: when first posting in the link noted above, that was my conclusion when verifying that my actual oil consumption was very modest .... but the occasional PO410 code comes in. A possible history of overfilling by previous ownership?
If there is a grain of reality to this, then overfilling can contribute to SAI issues on perfectly healthy engines: when first posting in the link noted above, that was my conclusion when verifying that my actual oil consumption was very modest .... but the occasional PO410 code comes in. A possible history of overfilling by previous ownership?
10-08-2008, 05:47 PM
#20
Three Wheelin'
RE: GarthS,
Good point but there's one major ingredient (well, maybe more than one) that's required in order for a 'full filling of oil' to significantly contribute to blocking the SAI passages via 'oil aspiration'.
I put forward that THAT ingredient is *how tight the engine tolerances are* - in particular the piston rings and, yes, the valves.
A brand new engine -filled to the brim with oil- IMHO would be LESS likely, than a 'well worn engine', to pass 'atomized oil' thru' the exhaust valves. A brand new engine is 'tight'.
Similarly, a nicely warmed-up engine - even one with 'miles' on it -- (where the metal has all EXPANDED - consequently closing (or minimizing) 'wear gaps' - would, IMHO, also be *less* likely.
I like discussing stuff like this with you guyz, coz it makes us all think and not just take, as God's word, that 'worn valves' are ONLY cause. Surely, by the time the valves are totally shot, there are other parts of the engine that are well worn too? But the valves get the bum rap because they are so 'slight' that any wear, on them, shows up as big-time wear.
Personally, I think the magic elixir to preventing SAI problems lies in
i) NOT 'constantly topping up' your oil level but rather keeping it ever so slightly below 'full'
ii) Letting the engine warm up gently well before you decide to 'floor it' - so that metal-expansion has had time to do it's thing
iii) Replace the SAI checkvalve every 30K miles
iv) As the engine ages ...switch to a slighly heavier grade oil ...and/or add a quart of Lucas in your 'normal' indy-and-maintenance-manual-endorsed grade.
My $0.02,
Gerry
Good point but there's one major ingredient (well, maybe more than one) that's required in order for a 'full filling of oil' to significantly contribute to blocking the SAI passages via 'oil aspiration'.
I put forward that THAT ingredient is *how tight the engine tolerances are* - in particular the piston rings and, yes, the valves.
A brand new engine -filled to the brim with oil- IMHO would be LESS likely, than a 'well worn engine', to pass 'atomized oil' thru' the exhaust valves. A brand new engine is 'tight'.
Similarly, a nicely warmed-up engine - even one with 'miles' on it -- (where the metal has all EXPANDED - consequently closing (or minimizing) 'wear gaps' - would, IMHO, also be *less* likely.
I like discussing stuff like this with you guyz, coz it makes us all think and not just take, as God's word, that 'worn valves' are ONLY cause. Surely, by the time the valves are totally shot, there are other parts of the engine that are well worn too? But the valves get the bum rap because they are so 'slight' that any wear, on them, shows up as big-time wear.
Personally, I think the magic elixir to preventing SAI problems lies in
i) NOT 'constantly topping up' your oil level but rather keeping it ever so slightly below 'full'
ii) Letting the engine warm up gently well before you decide to 'floor it' - so that metal-expansion has had time to do it's thing
iii) Replace the SAI checkvalve every 30K miles
iv) As the engine ages ...switch to a slighly heavier grade oil ...and/or add a quart of Lucas in your 'normal' indy-and-maintenance-manual-endorsed grade.
My $0.02,
Gerry
