OVERHEATING ISSUE - Fans working or not ?
08-24-2007 | 01:43 PM
#17
Drifting
Joined: Aug 2006
Posts: 2,508
Likes: 24
Okay, must be a lot of lawyers in this room. Let me be more precise:
A warm engine will not thin the oil enough so that operating temperatures in a six year old car suddenly rise and oil pressures drop to levels not routinely seen in the previous six years without some change in circumstance. For greater certainty, as lawyers say, I am not talking about the difference between cold oil and warm oil, where there is very obviously some change. I am talking about oil at normal engine operating temperatures. In a healthy engine, oil that's already fully warm is highly unlikely to lose viscosity as temperatures rises so as to both reduce pressures and contribute to further increases in operating temperature.
Does that help?
A warm engine will not thin the oil enough so that operating temperatures in a six year old car suddenly rise and oil pressures drop to levels not routinely seen in the previous six years without some change in circumstance. For greater certainty, as lawyers say, I am not talking about the difference between cold oil and warm oil, where there is very obviously some change. I am talking about oil at normal engine operating temperatures. In a healthy engine, oil that's already fully warm is highly unlikely to lose viscosity as temperatures rises so as to both reduce pressures and contribute to further increases in operating temperature.
Does that help?
08-24-2007 | 01:51 PM
#18
Race Car
Joined: Apr 2004
Posts: 4,159
Likes: 8
From: Chicagoland
Don't put words in my mouth. Here are facts:
1. I have the same engine as the poster.
2. I run Mobil 0W40, as recommended by Porsche.
3. My oil pressure is higher than half a bar at idle, even with the engine at 100 degrees C.
4. My oil pressure is much higher than 3 bars at 5,000 rpm, again, regardless of temperature.
5. The poster was not asking about a normal operating condition. He was asking about a change he noticed, a change that did not seem to coincide with switching oils.
It is therefore simple, pure logic that something is wrong, and that something is not his long standing choice of oil or lack of a third radiator or fan mod. If nothing changed in his circumstances, then something has gone wrong in the motor. This is immutable.
Stop preaching your same old story and help the guy out. If you can't help, then holster it until the next time someone asks about oil viscosities.
1. I have the same engine as the poster.
2. I run Mobil 0W40, as recommended by Porsche.
3. My oil pressure is higher than half a bar at idle, even with the engine at 100 degrees C.
4. My oil pressure is much higher than 3 bars at 5,000 rpm, again, regardless of temperature.
5. The poster was not asking about a normal operating condition. He was asking about a change he noticed, a change that did not seem to coincide with switching oils.
It is therefore simple, pure logic that something is wrong, and that something is not his long standing choice of oil or lack of a third radiator or fan mod. If nothing changed in his circumstances, then something has gone wrong in the motor. This is immutable.
Stop preaching your same old story and help the guy out. If you can't help, then holster it until the next time someone asks about oil viscosities.
You may want to consider looking at YOUR OWN engine as having an oil pressure of about 3 bar when at 5000 rpm is way to low. Try looking for about 5 bar.
As far as the orginal poster asking only about "normal" operating conditions, he is simply off base stating that he normally had a coolant temperature between 84-85C. This is impossible for the 3.4 engine in ANY conditions and I was simply making him aware of the fact that those temps should not be his target. Therefore, the "change" he noticed does not exist as reported.
Finally, many 3.4 engine have a hot idle oil pressure very close to 1/2 bar when running 0W40. This is why so many have switched from the Mobil Water to a better oil. Take an actual reading of yours when your engine temp reach 110C+/- bar. These engine temps are quite common for the 3.4 in sunny, hotter climates while driving around town.
08-24-2007 | 02:05 PM
#19
Drifting
Joined: Aug 2006
Posts: 2,508
Likes: 24
I sure hope your hot idle oil pressure is above 1/2 bar. No engine should run less than 1 bar and even that is on the dangerous side. 1.4 bar is much safer and any good engine will produce that pressure. If it doesn't you are running too thin an oil to maintain proper bearing clearances. No 3.4 engine will produce an idle oil preasure of 1.4 bar when engine temps are at 100C+ when running Mobil 0W40. That is just a fact. Forget the Porsche gauge and look at the actual pressure.
You may want to consider looking at YOUR OWN engine as having an oil pressure of about 3 bar when at 5000 rpm is way to low. Try looking for about 5 bar.
As far as the orginal poster asking only about "normal" operating conditions, he is simply off base stating that he normally had a coolant temperature between 84-85C. This is impossible for the 3.4 engine in ANY conditions and I was simply making him aware of the fact that those temps should not be his target. Therefore, the "change" he noticed does not exist as reported.
Finally, many 3.4 engine have a hot idle oil pressure very close to 1/2 bar when running 0W40. This is why so many have switched from the Mobil Water to a better oil. Take an actual reading of yours when your engine temp reach 110C+/- bar. These engine temps are quite common for the 3.4 in sunny, hotter climates while driving around town.
You may want to consider looking at YOUR OWN engine as having an oil pressure of about 3 bar when at 5000 rpm is way to low. Try looking for about 5 bar.
As far as the orginal poster asking only about "normal" operating conditions, he is simply off base stating that he normally had a coolant temperature between 84-85C. This is impossible for the 3.4 engine in ANY conditions and I was simply making him aware of the fact that those temps should not be his target. Therefore, the "change" he noticed does not exist as reported.
Finally, many 3.4 engine have a hot idle oil pressure very close to 1/2 bar when running 0W40. This is why so many have switched from the Mobil Water to a better oil. Take an actual reading of yours when your engine temp reach 110C+/- bar. These engine temps are quite common for the 3.4 in sunny, hotter climates while driving around town.
I said, my oil pressure IS way above those values. It's the poster's who aren't. My engine operating temps as read from OBD are in the high 90s, fully warmed, under most circumstances, and as high as 105 on a hot day idling in traffic.
As for the broader oil question, you should do what makes you comfortable. I've got a 3.4 with 82,000km on it, running 0W40 as long as Porsche has been recommending it, as an urban daily driver. I've passed a compression and leakdown test with flying colours, passed oil tests with flying colours, and the car runs like a champ. Life's too short to invent stuff to worry about, and I'm not going to change what works.