Best viscosity for hot temperature
06-06-2003, 07:24 PM
#16
jhb,
Disclimer: I do not claim to be an expert on this and am only passing along information that I received at a seminar this year on this very topic.
This is an interesting and on going debate among Porsche guru's. There are many different opinions. There is no questions that the 0w40 should be used for the new 996 and 986 engines. However the answer is much murkier when you look at the 993 because of the limited availability of the 0w40 Mobil 1 in the US until recently.
I asked this exact question at the Visit 2.0 in an open floor tech seminar with the likes of Bruce Anderson, a couple of the PCA tech representatives, some very well respected tuners and a director of a race team. They all agreed that you should change your oil on a much more frequent basis than what Porsche recommends, no matter what viscosity you use. It came out that the oil change recommendations come from a lot of legal, regulatory and environmental issues on the "total pollution" of a vehicle and not necessarily what is best for the longevity of the engine. Also the more frequently your oil temps cycle through extreme temperatures the more often you should change the oil.
Bruce Anderson's short answer was that the 0w40 was better on the lifters and valve train in the 993 engine than the 15w50. 0w40 made things run quieter and allowed for less wear on cold start ups and was probably the best choice. Under hellaciously hot conditions 15w50 was probably better.
Another issue that came up was that with the advance of the synthetic oils that break down under higher temperatures was not as great as it use to be and that frequent oil changes would go a long way in protecting your engine.
Disclimer: I do not claim to be an expert on this and am only passing along information that I received at a seminar this year on this very topic.
This is an interesting and on going debate among Porsche guru's. There are many different opinions. There is no questions that the 0w40 should be used for the new 996 and 986 engines. However the answer is much murkier when you look at the 993 because of the limited availability of the 0w40 Mobil 1 in the US until recently.
I asked this exact question at the Visit 2.0 in an open floor tech seminar with the likes of Bruce Anderson, a couple of the PCA tech representatives, some very well respected tuners and a director of a race team. They all agreed that you should change your oil on a much more frequent basis than what Porsche recommends, no matter what viscosity you use. It came out that the oil change recommendations come from a lot of legal, regulatory and environmental issues on the "total pollution" of a vehicle and not necessarily what is best for the longevity of the engine. Also the more frequently your oil temps cycle through extreme temperatures the more often you should change the oil.
Bruce Anderson's short answer was that the 0w40 was better on the lifters and valve train in the 993 engine than the 15w50. 0w40 made things run quieter and allowed for less wear on cold start ups and was probably the best choice. Under hellaciously hot conditions 15w50 was probably better.
Another issue that came up was that with the advance of the synthetic oils that break down under higher temperatures was not as great as it use to be and that frequent oil changes would go a long way in protecting your engine.
06-06-2003, 08:15 PM
#18
</font><blockquote><font size="1" face="Verdana,Tahoma,Helvetica">quote:</font><hr /><font size="2" face="Verdana,Tahoma,Helvetica">Originally posted by jhb:
<strong>I thought the "w" number referred to cold viscosity and the 2nd number was for warm viscosity. If that is the case, how could a 0w-40 and 15w-50 be that different once warm? Obviously, the 0w-40 will flow faster when cold.
</strong></font><hr /></blockquote><font size="2" face="Verdana,Tahoma,Helvetica">Well, it all depends on the temperature versus viscosity curve. I’ve yet to find one of these (I searched the net for a while, but gave up). If the oil is say 40W at 150 degrees and higher, then the 10W-40 will remain at 40 weight but the 50 weight oil will get heaver as the temperature passes 150. It will become 50 weight at whatever temp that occurs. Say this happens at 180. In this case, 15W-50 will be the same as 0W-40 up to 150 degrees, and then gradually get thicker, until it reaches 180 degrees where it will be 50 weight. Remember, I’ve never seen a chart, so I’m making these numbers up to make the point.
The same could be true when cold. How cold does it have to get for the 0W-40 to actually be 0 weight oil? Or in the real world, when I start my motor on a 60 degree morning, what viscosity is the oil at 60 degrees? Say the viscosity/temperature curve says that at 60 degrees, the oil is 20 weight. In this case, 0W-40 and 15W-50 will be the same. But if the oil is 5 weight at 60 degrees, well you get the picture.
If anyone has a temperature/viscosity chart, I’d love to see it.
Another possibility is to mix viscosities of oil. According to the Mobil 1 web site, this is totally fine (I wouldn’t even think of mixing different brands, though). I did this on my most recent oil change. I used three quarts of 0W-40 and the rest 15W-50. Apparently, the resulting viscosity is pretty much, but not exactly, the mathematical weighting of the mixing. So if the total capacity of a 993 is 12 quarts, mixing 3 quarts of 0W-40 gives you 11.75W-47.5 oil. Mixing 4 quarts in would give you 9.9W-46.6. Both of these give you a much thinner oil for startup, yet still provide almost the protection of a 50 weight at higher temperatures.
Tom
’95 993
<strong>I thought the "w" number referred to cold viscosity and the 2nd number was for warm viscosity. If that is the case, how could a 0w-40 and 15w-50 be that different once warm? Obviously, the 0w-40 will flow faster when cold.
</strong></font><hr /></blockquote><font size="2" face="Verdana,Tahoma,Helvetica">Well, it all depends on the temperature versus viscosity curve. I’ve yet to find one of these (I searched the net for a while, but gave up). If the oil is say 40W at 150 degrees and higher, then the 10W-40 will remain at 40 weight but the 50 weight oil will get heaver as the temperature passes 150. It will become 50 weight at whatever temp that occurs. Say this happens at 180. In this case, 15W-50 will be the same as 0W-40 up to 150 degrees, and then gradually get thicker, until it reaches 180 degrees where it will be 50 weight. Remember, I’ve never seen a chart, so I’m making these numbers up to make the point.
The same could be true when cold. How cold does it have to get for the 0W-40 to actually be 0 weight oil? Or in the real world, when I start my motor on a 60 degree morning, what viscosity is the oil at 60 degrees? Say the viscosity/temperature curve says that at 60 degrees, the oil is 20 weight. In this case, 0W-40 and 15W-50 will be the same. But if the oil is 5 weight at 60 degrees, well you get the picture.
If anyone has a temperature/viscosity chart, I’d love to see it.
Another possibility is to mix viscosities of oil. According to the Mobil 1 web site, this is totally fine (I wouldn’t even think of mixing different brands, though). I did this on my most recent oil change. I used three quarts of 0W-40 and the rest 15W-50. Apparently, the resulting viscosity is pretty much, but not exactly, the mathematical weighting of the mixing. So if the total capacity of a 993 is 12 quarts, mixing 3 quarts of 0W-40 gives you 11.75W-47.5 oil. Mixing 4 quarts in would give you 9.9W-46.6. Both of these give you a much thinner oil for startup, yet still provide almost the protection of a 50 weight at higher temperatures.
Tom
’95 993
06-06-2003, 08:51 PM
#19
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</font><blockquote><font size="1" face="Verdana,Tahoma,Helvetica">quote:</font><hr /><font size="2" face="Verdana,Tahoma,Helvetica">Originally posted by 96P993:
<strong>Brian would Texas summers be in the "hellaciously hot" category??</strong></font><hr /></blockquote><font size="2" face="Verdana,Tahoma,Helvetica">Most certainly! If you do an archive search you can see one of my posts regarding the condition that the 0-40 oil put by the dealer, came out of my car... In short I will never use anything else BUT 15-50 on my cars. Regarding the lifter noise, and interesting fact is that I used to have the "dealer" oil in my BMW and had extensive lifter noise at start up if the car was standing for a couple of days. Switched to the same 15-50 Mobil1 and the noise is gone. Go figure...
<strong>Brian would Texas summers be in the "hellaciously hot" category??</strong></font><hr /></blockquote><font size="2" face="Verdana,Tahoma,Helvetica">Most certainly! If you do an archive search you can see one of my posts regarding the condition that the 0-40 oil put by the dealer, came out of my car... In short I will never use anything else BUT 15-50 on my cars. Regarding the lifter noise, and interesting fact is that I used to have the "dealer" oil in my BMW and had extensive lifter noise at start up if the car was standing for a couple of days. Switched to the same 15-50 Mobil1 and the noise is gone. Go figure...
06-08-2003, 12:01 AM
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</font><blockquote><font size="1" face="Verdana,Tahoma,Helvetica">quote:</font><hr /><font size="2" face="Verdana,Tahoma,Helvetica">Originally posted by Robert Linton:
<strong>I might consider 10W60 -- Castrol RS or Shell Ultra Helix -- and I would change oil and filters every 3000 race miles (maximum) and every 7500 street miles!</strong></font><hr /></blockquote><font size="2" face="Verdana,Tahoma,Helvetica">Robert,
Who would you source the 10w60 through? I doubt WalMart has it in stock <img border="0" title="" alt="[Wink]" src="wink.gif" />
<strong>I might consider 10W60 -- Castrol RS or Shell Ultra Helix -- and I would change oil and filters every 3000 race miles (maximum) and every 7500 street miles!</strong></font><hr /></blockquote><font size="2" face="Verdana,Tahoma,Helvetica">Robert,
Who would you source the 10w60 through? I doubt WalMart has it in stock <img border="0" title="" alt="[Wink]" src="wink.gif" />
06-08-2003, 01:07 AM
#23
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Tom -
None of the motor oils actually get thicker (higher viscosity) as they get hotter. They all get thinner. Synthetic oils, and those with 'viscosity improvers', just don't thin out as much as the temperature rises.
Now many of the extreme range synthetic oils also have viscosity improvers added to them - that is how you get 0W-40, 5W-50, and 10W-60 oils. They are great general use oils, but the problem is that over time the viscosity improvers, which are very long chain hydrocarbons that unfold at higher temperatures, break down more quickly than the base oil under high shear conditions (that would be Danny J. running around at 7200 rpm in Houston all summer). The result is this oil becomes thinner at the higher temperatures than when it was fresh.
So if you want to use these super extended range synthetics, it might be prudent to change your oil more often to be sure it is still 'good'. The 15W-50 synthetic oil from Mobil 1 (and the 5W-30) might have no or very little viscosity improvers in them, and they may remain more stable under severe use than the extended range synthetics.
Chip
None of the motor oils actually get thicker (higher viscosity) as they get hotter. They all get thinner. Synthetic oils, and those with 'viscosity improvers', just don't thin out as much as the temperature rises.
Now many of the extreme range synthetic oils also have viscosity improvers added to them - that is how you get 0W-40, 5W-50, and 10W-60 oils. They are great general use oils, but the problem is that over time the viscosity improvers, which are very long chain hydrocarbons that unfold at higher temperatures, break down more quickly than the base oil under high shear conditions (that would be Danny J. running around at 7200 rpm in Houston all summer). The result is this oil becomes thinner at the higher temperatures than when it was fresh.
So if you want to use these super extended range synthetics, it might be prudent to change your oil more often to be sure it is still 'good'. The 15W-50 synthetic oil from Mobil 1 (and the 5W-30) might have no or very little viscosity improvers in them, and they may remain more stable under severe use than the extended range synthetics.
Chip
06-13-2003, 01:34 AM
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Being oil-cooled, it is imperative that a 993 engine (or other o/c Porsche negines for that matter) get the right oil for the prevailing driving conditons. Oil viscosity, like 10W40, determines the viscosity of oil at cold start (10) and at operating temperature (40). n a cold climate, you want to ensure that the cold start qualities are appropriate, i.e. as low as possible. Anything 0Wxx or 5Wxx is ideal for 993's . In a hot climate, you need to focus on the running temperature vistcosity index. Ideal for the tropics, for instance, is anything above xxW50, preferably xxW60. In a perfect world, I woul drecommend an oil that doesn't exist, a 0W60. So, if your concerned about running your 993 in a hot climate zone, I strongly recommend a 10W60.
06-14-2003, 07:04 AM
#26
I recently put 0w40 in my 996TT. It seemed thicker than I expected. I've always believed in thick oil but I've changed my opinion. The higher flow rate of thinner oil will cool better. It also drains back to the oil pan faster to prevent starvation under high G loads.
Castrol synthetic comes in 5w50.
Non turbo Porsches are generally easy on oil. They have big oil coolers, and high capacity dry sump systems. The valve springs are relatively light so cam wear is not an issue. The dry sump prevents oil foaming also.
Castrol synthetic comes in 5w50.
Non turbo Porsches are generally easy on oil. They have big oil coolers, and high capacity dry sump systems. The valve springs are relatively light so cam wear is not an issue. The dry sump prevents oil foaming also.
