Oil: Opening up the can of worms
03-03-2009, 10:59 AM
#31
Three Wheelin'
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03-03-2009, 11:08 AM
#32
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Simple oil rules:
1. Buy a good synthetic
2. Pick a weight that matches your driving / usage / climate
3. Stay away from all GF-4 oils
As for the different weights, you must understand this first (from Blackstone Labs):
http://www.blackstone-labs.com/oil_viscosity.html
What does this mean? 0w-40 is really a zero weight oil with additives to make it act like a 40 weight oil at 210 degrees fahrenheit.
So "in theory" a 20w-40 might be a higher viscosity at 150 degrees than 0w-40. While they will both be the same at 210......
Clear as mud
1. Buy a good synthetic
2. Pick a weight that matches your driving / usage / climate
3. Stay away from all GF-4 oils
As for the different weights, you must understand this first (from Blackstone Labs):
The difference between multi-grades and straight-weight oils is simply the addition of a viscosity improving (VI) additive. The most common grade of automotive oil in use today is the 5W/30, which is a mineral oil refined to the SAE 5 weight viscosity range containing the usual cleaning and anti-wear additives, then blended with a VI additive that should leave it reading in the SAE 30 weight range when at the higher (210F) temperature. The advantage to the multi-weight is, when starting the engine, the multi-viscosity oil has the thickness of an SAE 5 weight, which allows the engine to spin over more easily.
What does this mean? 0w-40 is really a zero weight oil with additives to make it act like a 40 weight oil at 210 degrees fahrenheit.
So "in theory" a 20w-40 might be a higher viscosity at 150 degrees than 0w-40. While they will both be the same at 210......
Clear as mud
03-03-2009, 11:09 AM
#33
Three Wheelin'
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03-03-2009, 11:17 AM
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Sorry if I misunderstood -- it still reads to me that way, but you may have intended it differently.
But it is not a "tired old argument." It is simply misinformation (which I thought you were repeating.)
I'm glad that's been clarified at least. There's alot of misinformation and mythology about oil -- a complicated subject, we all agree. Some of that misinformation and mythology leads some people make poor decisions about how to lubricate their engines.
Now, I'm the guy who says that there are times when it is silly to double-guess experts in their fields on technical subjects, unless you have a comparable level of expertise yourself. A little knowledge can be a dangerous thing, and all that. So my place in this thread is to wave the flag that says "the guys in Stuttgart that designed your engine probably knew a thing or two about their subject. There is a certain built-in weight of authority in the handbook recommendations that are going to be hard to match from other sources." Dr Haas and all.
That's all. I don't claim to be an oil expert. In fact, that's exactly my point...
So, Joonas: the only thing I have to say about the 10psi/1000rpm rule is I have heard of it, and, more importantly, I'm sure the guys in Stuttgart had heard of it too when they came up with their recommendations.
But it is not a "tired old argument." It is simply misinformation (which I thought you were repeating.)
I'm glad that's been clarified at least. There's alot of misinformation and mythology about oil -- a complicated subject, we all agree. Some of that misinformation and mythology leads some people make poor decisions about how to lubricate their engines.
Now, I'm the guy who says that there are times when it is silly to double-guess experts in their fields on technical subjects, unless you have a comparable level of expertise yourself. A little knowledge can be a dangerous thing, and all that. So my place in this thread is to wave the flag that says "the guys in Stuttgart that designed your engine probably knew a thing or two about their subject. There is a certain built-in weight of authority in the handbook recommendations that are going to be hard to match from other sources." Dr Haas and all.
That's all. I don't claim to be an oil expert. In fact, that's exactly my point...
So, Joonas: the only thing I have to say about the 10psi/1000rpm rule is I have heard of it, and, more importantly, I'm sure the guys in Stuttgart had heard of it too when they came up with their recommendations.
03-03-2009, 11:20 AM
#36
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Yes, for daily driving but we are not talking about it right now.
03-03-2009, 11:26 AM
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I've never seen the qualification for the Porsche recommendations that "this is for daily driving only". The operating temperature of a track car engine is close to the operating temperature of a daily driver (or else you don't drive for very long), and so the oil flow characteristics are going to be similar.
I think you might want to change your oil a bit more regularly, perhaps.
I think you might want to change your oil a bit more regularly, perhaps.
03-03-2009, 11:27 AM
#40
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Nothing to explain - it's trial and error.
If you really care that much, start sending in oil samples to BlackStone labs and see what's going on. Anything else is just guesswork and / or opinions with very little facts.
If I run 5w-40 in my 928 the lifters will clack like crazy in July once everything is warmed up, so I run 20w-50. My neighbor has a 928 with the same engine, he uses 10w-40 with no problems.
In a full out race car I would use straight weight oil.
In theory the greater difference between the two numbers the more / faster the oil will break down (and come closer to the lower number even at full temperature).
I would (actually I am) installing an oil temperature probe. I might install two, one where the oil leaves the filter and another on the pan.
Why?
If you are not even warming up the oil to full 210 degrees (or more) in theory you are not even reaching the second number.
I'm going to assume the car your avatar.
Define "heavy track use".
Is your oil cooler stock?
Are you relying on the stock oil pressure sender?
Do you have any type of oil temperature gauge installed?
Are you using an accusump?
These question are far more important to your track car then what weight / brand oil to use.
If you really care that much, start sending in oil samples to BlackStone labs and see what's going on. Anything else is just guesswork and / or opinions with very little facts.
If I run 5w-40 in my 928 the lifters will clack like crazy in July once everything is warmed up, so I run 20w-50. My neighbor has a 928 with the same engine, he uses 10w-40 with no problems.
In a full out race car I would use straight weight oil.
In theory the greater difference between the two numbers the more / faster the oil will break down (and come closer to the lower number even at full temperature).
I would (actually I am) installing an oil temperature probe. I might install two, one where the oil leaves the filter and another on the pan.
Why?
If you are not even warming up the oil to full 210 degrees (or more) in theory you are not even reaching the second number.
I'm going to assume the car your avatar.
Define "heavy track use".
Is your oil cooler stock?
Are you relying on the stock oil pressure sender?
Do you have any type of oil temperature gauge installed?
Are you using an accusump?
These question are far more important to your track car then what weight / brand oil to use.
03-03-2009, 11:29 AM
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I've never seen the qualification for the Porsche recommendations that "this is for daily driving only". The operating temperature of a track car engine is close to the operating temperature of a daily driver (or else you don't drive for very long), and so the oil flow characteristics are going to be similar.
I think you might want to change your oil a bit more regularly, perhaps.
I think you might want to change your oil a bit more regularly, perhaps.
03-03-2009, 11:35 AM
#43
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Please find the section that recommends the oil for track use!
Engine oil pressure is shown in bars. At 5.000 rpm, with the engine at normal operating temperature (approx. 90°C / 194°F), the pressure should be approx. 4 bar. A slight drop in oil pressure is normal under certain operating conditions such as prolonged highway driving in hot weather.
Hot weather does not qualify track usage.
Oil weight table gives outside temp ranges and oil weights but there is no "driving constantly near rev limiter" sugestions.
Engine oil pressure is shown in bars. At 5.000 rpm, with the engine at normal operating temperature (approx. 90°C / 194°F), the pressure should be approx. 4 bar. A slight drop in oil pressure is normal under certain operating conditions such as prolonged highway driving in hot weather.
Hot weather does not qualify track usage.
Oil weight table gives outside temp ranges and oil weights but there is no "driving constantly near rev limiter" sugestions.
03-03-2009, 11:35 AM
#44
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I know "regular" track cars that see 250-280+ degree oil temps on the track. If your street car is seeing these temps, something is really wrong.
03-03-2009, 12:04 PM
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Let me ask another question: Is Mobil 1 5w 50 (which is recommended for DD) completely unsuitable for 944 track car use because of the higher transient oil temps that you point out?