What weight engine oil?
10-06-2010, 05:39 PM
#31
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high revving large displacement four cylinder engines put tremendous pressure on rod bearings. when they wear, you're basically screwed because you need oil that will fill the now enlarged space between the metal on metal surfaces.
it's a tug of war in a (180 degrees X 4) design... beween the pistons/connecting rods and the crank dampeners/harmonic balancer ---
one reason why our cars vibrate at certain resonant frequencies even on the smoothest freeways.
for example, the (90 degrees X 8) design of the V8 where there is always a piston turning entering the "power stroke" as another departs.... this creates an environment that is much more gentle the internal components and accessory components, (at least in theory, but, of course V8 engines apply tremendous force to the main bearings)...
from wiki:
"The inline-four layout .... despite its simplicity.... suffers from a secondary imbalance which causes minor vibrations in smaller engines. These vibrations become worse as engine size and power increase...."
"piston acceleration and deceleration are greater in the top half of the crankshaft rotation than in the bottom half, because the connecting rods are not infinitely long, resulting in a non sinusoidal motion. As a result, two pistons are always accelerating faster in one direction, while the other two are accelerating more slowly in the other direction, which leads to a secondary dynamic imbalance that causes an up-and-down vibration at twice crankshaft speed. This imbalance is tolerable in a small, low-displacement, low-power configuration, but the vibrations get worse with increasing size and power...."
the 968 with it's large cylinders might be the worst of all. i love the engine for what it can do -
but, the vibrations are pretty annoying, and can also contribute to shorter life of the accessory components (not just the destruction of the motor mounts). and there's so little power in the lower/mid rpm range...
i've considered stopping the expensive maintenance program... and (just changing oil filters and adding the synthetic oil), maybe do 1 more set of belts about 50~60 k miles down the road @ about 165-180 K miles. and then, no more belts or oil changes until the thing blows up.
but in fact, i may indeed change out the rod bearings, and keep running the slightly thinner synthetic oil.
http://www.youtube.com/watch?v=Hhc6xM0wjKQ
Last edited by odurandina; 10-06-2010 at 07:21 PM.
10-06-2010, 06:57 PM
#32
Rennlist Member
Porsche went to a lot of trouble to assure a constant range of oil temperatures in the engine (via the oil cooler, which also heats up the oil quickly from a cold start). Using a thinner oil in the winter has benefit for perhaps 3 minutes each time you do a cold start, the whole rest of the trip you have lower viscosity than desired. Starters are cheaper and easier to replace than rod bearings.
AFAIK the #2 rod bearing issues have nothing to do with crankshaft vibrations, which affect main bearings. From what I've read on here, the #2 problems are due to lack of an adequate oil film (inadequate oil pressure/flow/cooling).
AFAIK the #2 rod bearing issues have nothing to do with crankshaft vibrations, which affect main bearings. From what I've read on here, the #2 problems are due to lack of an adequate oil film (inadequate oil pressure/flow/cooling).
10-07-2010, 09:03 AM
#33
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Hi Dogberri , stick with what Porsche printed in the owners manual that came with your 944 , on the oil viscosity page within the owners manual there is the shaded look at me section , the first cab off the rank is the ambient temp range of minus 10 deg cel to unlimited high temps , Porsche states that the recommended oil viscosity is either a 20w-50 or a 15w - 50 .
A few items to ponder }
A) The 944 is not from this century in regards to modern engine design and the thinner viscosity engine oils that go with that , in fact the 944 engine design goes well back into last century and has a few small flaws that can be kept in check if you stick with the recommendations to what Porsche printed in the owners manual
Question = What flaws ?
Answer = first of all , no 2 big end journal( con rod big end bearing) has an issue with oil pressure a high RPM , basically it starves due to engine/ crank design and this becomes very apparent when the wrong oil is used in relation to ambient temps( read too thinner oil) , naturally this results in a destroyed crankshaft and no 2 con rod or worse a destroyed crankcase as well .
However if you stick to the recommendation in the owners manual and always stay on the high side of the viscosity then the no 2 big end ( con rod big end bearing ) issue never rears its ugly head , naturally we need a good set of big end ( con rod big end bearings) to start with .
B) ZDDP , the other advantage with 20w-50 and most 15w-50 engine oils is that they are relegated for the use in last century car engines( just like the 944) and they are not subject to the amount of reduction in ZDDP ( anti wear)because of emission protocols ( ACEA etc ) as this century petrol ( gas USA speak) engines are , this is very important to engines like the 944 because of the high loaded flat tappet design of the overhead camshaft design that the 944 has , I have nearly lost count how many cams & lifters we have replaced because of the use of lower viscosity oils that also had the misfortune to have low levels of ZDDP in the last 12 + years or so ( 944 , 944S , 944S2 , 951 , 928 , 928S , 928S4 , 928GT, 928GTS ) & cams and rocker shafts +excessive valve guide wear in 911SC , 930 , 911 3.2, 964 , 993 etc , these were all avoidable if the ZDDP was of decent levels and decent oil viscosity in relation to the last century technology , which works fine if respected for what it is .
But of course its all in the owners manual & put there by the very people who designed these engines all those decades ago
Remember the oil viscosity index has not changed, what was a 20w-50 then is a 20w-50 now and so on .
Regards
Bruce Buchanan
A few items to ponder }
A) The 944 is not from this century in regards to modern engine design and the thinner viscosity engine oils that go with that , in fact the 944 engine design goes well back into last century and has a few small flaws that can be kept in check if you stick with the recommendations to what Porsche printed in the owners manual
Question = What flaws ?
Answer = first of all , no 2 big end journal( con rod big end bearing) has an issue with oil pressure a high RPM , basically it starves due to engine/ crank design and this becomes very apparent when the wrong oil is used in relation to ambient temps( read too thinner oil) , naturally this results in a destroyed crankshaft and no 2 con rod or worse a destroyed crankcase as well .
However if you stick to the recommendation in the owners manual and always stay on the high side of the viscosity then the no 2 big end ( con rod big end bearing ) issue never rears its ugly head , naturally we need a good set of big end ( con rod big end bearings) to start with .
B) ZDDP , the other advantage with 20w-50 and most 15w-50 engine oils is that they are relegated for the use in last century car engines( just like the 944) and they are not subject to the amount of reduction in ZDDP ( anti wear)because of emission protocols ( ACEA etc ) as this century petrol ( gas USA speak) engines are , this is very important to engines like the 944 because of the high loaded flat tappet design of the overhead camshaft design that the 944 has , I have nearly lost count how many cams & lifters we have replaced because of the use of lower viscosity oils that also had the misfortune to have low levels of ZDDP in the last 12 + years or so ( 944 , 944S , 944S2 , 951 , 928 , 928S , 928S4 , 928GT, 928GTS ) & cams and rocker shafts +excessive valve guide wear in 911SC , 930 , 911 3.2, 964 , 993 etc , these were all avoidable if the ZDDP was of decent levels and decent oil viscosity in relation to the last century technology , which works fine if respected for what it is .
But of course its all in the owners manual & put there by the very people who designed these engines all those decades ago
Remember the oil viscosity index has not changed, what was a 20w-50 then is a 20w-50 now and so on .
Regards
Bruce Buchanan
Listen to a Porsche trained mechanic above who has been working on these cars for over 30 years. Don't listen to the people who think that because Porsche America 'apporves' oils like M1 0-30w as a good oil for our cars, therefore that is 100% irrefutable law. It ain't. As you research some more on this matter you will find that Oil is a religion.
Here is a very good thread on Pelican with contributions from Authorities on our cars. It's a long and evolving thread, but you'll get the gist of it. Most oils nowdays are made for fuel economy reasons. Our cars aren't designed for that style of lubricant. We need a better form of protection and that requires high enough ZDDP and thick enough film strength. A thin 0w oil won't offer that insurance, especially when your car gets hot.
http://tiny.cc/zt5f9
10-07-2010, 10:07 AM
#34
Captain Obvious
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I'll add some of my experience here.
Its starting to get low temps at night, we've even had a heavy frost last Monday.
I run 20W50 all the time, but I thought for ****s and gigs I'd try 15W40 for the cooler months until I park my car. Lots of guys do this from what I've read on the plethera of "what oil" threads.
So, I swapped out the oil.
Monday when I started the car (it was very cool that morning with the frost) and my friggin lifters ticked away almost 5 minutes until the pressure built up in them. They were quiet the rest of the day driving.
The next morning, no frost @ 10 degrees C, same thing again, not as long with lifter noise.
I thought to myself, no way, and drained the oil. I put 20W50 back in...and this morning with cool temps...NO LIFTER NOISE.
Go figure?
Its starting to get low temps at night, we've even had a heavy frost last Monday.
I run 20W50 all the time, but I thought for ****s and gigs I'd try 15W40 for the cooler months until I park my car. Lots of guys do this from what I've read on the plethera of "what oil" threads.
So, I swapped out the oil.
Monday when I started the car (it was very cool that morning with the frost) and my friggin lifters ticked away almost 5 minutes until the pressure built up in them. They were quiet the rest of the day driving.
The next morning, no frost @ 10 degrees C, same thing again, not as long with lifter noise.
I thought to myself, no way, and drained the oil. I put 20W50 back in...and this morning with cool temps...NO LIFTER NOISE.
Go figure?
10-07-2010, 11:06 AM
#36
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I've followed all the threads on the oil to use in a 944 but since I purchased the car, I've used Mobil 1 15-50 exclusively. I have never heard lifter tick and I'd like to keep it that way for as long as possible. I store the car for winter though, before the first snow, so I never run the car in extreme cold temps. My theory is if there are no problems, don't mess with success...
10-07-2010, 12:37 PM
#40
Administrator - "Tyson"
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No
That's even worse advice. No way I will ever run an oil with that wide of a viscosity spread in a car I care about.
At least not again. My 100% street driven 944S puked up a rod bearing on Castrol 5w-50.
No thank you
Most of us do not drive our cars when it's cold outside.
You also need to define "cold" which is not 40 degrees when it comes to modern engine oils.
As other people have suggested, you need to talk to experienced engine builders and mechanics who have seen the damage from using the wrong oil in these cars.
Post all the links you want about oil theory, doesn't mean squat to those of us that have seen results in real life.
At least not again. My 100% street driven 944S puked up a rod bearing on Castrol 5w-50.
No thank you
You also need to define "cold" which is not 40 degrees when it comes to modern engine oils.
As other people have suggested, you need to talk to experienced engine builders and mechanics who have seen the damage from using the wrong oil in these cars.
Post all the links you want about oil theory, doesn't mean squat to those of us that have seen results in real life.
10-07-2010, 12:49 PM
#41
Hey Man
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No....You also need to define "cold" which is not 40 degrees when it comes to modern engine oils.
As other people have suggested, you need to talk to experienced engine builders and mechanics who have seen the damage from using the wrong oil in these cars.
Post all the links you want about oil theory, doesn't mean squat to those of us that have seen results in real life.
As other people have suggested, you need to talk to experienced engine builders and mechanics who have seen the damage from using the wrong oil in these cars.
Post all the links you want about oil theory, doesn't mean squat to those of us that have seen results in real life.
10-07-2010, 05:32 PM
#43
Rennlist Member
^^ You are generally obtuse at the best of times. Ignorant at others. Keep using your water and leave the correct oil for us to use. Are you going to pay for the OPs motor when it destructs.....nope didn't think so.
10-07-2010, 05:52 PM
#44
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hey ?
Mick Fanning or Kelly Slater and the 10 million from Quicksilver ?
i've been schooled by one of the long time guys over the phone about oils this afternoon. if we were all around in a circle i'd be able to express one point of view about one place i do have some experience. about 180 k miles in my 2 ford escapes running 5w-20 over off-road in Mexico. that's a bias there about running the thin stuff.
i had an '87 944 S. ran 10w-40 on that car.
i wasn't aware there have been so many issues running the slightly thinner 40 weight oils on the cars until the past couple of threads.
10w-40 was the conventional wisdom for 4 cylinder cars back in the 1980s. that was a long time ago.
i guess that view has long since been crushed by the Porsche owners.
Mick Fanning or Kelly Slater and the 10 million from Quicksilver ?
i've been schooled by one of the long time guys over the phone about oils this afternoon. if we were all around in a circle i'd be able to express one point of view about one place i do have some experience. about 180 k miles in my 2 ford escapes running 5w-20 over off-road in Mexico. that's a bias there about running the thin stuff.
i had an '87 944 S. ran 10w-40 on that car.
i wasn't aware there have been so many issues running the slightly thinner 40 weight oils on the cars until the past couple of threads.
10w-40 was the conventional wisdom for 4 cylinder cars back in the 1980s. that was a long time ago.
i guess that view has long since been crushed by the Porsche owners.
10-07-2010, 06:08 PM
#45
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My excuses OD I personally think that this BS about oil is getting a little rediculous & that it migth steer peoples specially new guys coming on the forum in the wrong direction.My present car is the seven Porsches that I've owne since the 70s,they were all keep alive without mechanical issues by changing oil & filters every 5k miles maximum.The six one a 944 NA is still going strong afterr 27 yrs (never open the motor on that one neither) oil use in it was 20w50 exclusively & planning to do the same with my 968.We can stand here & debate brand vs brand __viscosity vs viscosity but it all come down to one thing ,if the oil you choose to run in your car years after years does the job stick with it.And there is one thing I will like OD to realize,do you know how many time over the period of 27 years my 944 was started in warm & cold weather ?? Answer hundred of time yet like mention it still going strong with no mechanical issues.