For those who are wondering when to use 0W-40 on our 993s.
08-27-2004, 01:17 PM
#16
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Edward,
Like your opinion. The same rationale can used in the "factory" recommendations for maintenance intervals for selected services. For example, 1st oil change at 15K, fuel filter at 50K...996 & 986 have even longer service intervals.
Like your opinion. The same rationale can used in the "factory" recommendations for maintenance intervals for selected services. For example, 1st oil change at 15K, fuel filter at 50K...996 & 986 have even longer service intervals.
08-27-2004, 02:12 PM
#17
Passed On
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Been using the Mobil 1 0W40 for several years. Car has 84K miles and runs like a top. If I ever start driving regularly thru Death Valley, maybe I'll switch to 15W50; till then I'll stick to 0W40. If the factory & Bruce Anderson both recommend it, I'll follow their advice.
I gave up on the Castrol 5W50 several years ago when I read a test comparison report saying it tended to break down under high stress conditions. Mobil 1 15W50 didn't.
I gave up on the Castrol 5W50 several years ago when I read a test comparison report saying it tended to break down under high stress conditions. Mobil 1 15W50 didn't.
08-28-2004, 03:12 AM
#18
RL Technical Advisor
Lexpilot:
Its been fun reviewing this thread since its started back in February.
IMHO, a clarification might be needed here. The operating conditions inside the air-cooled 993 engines and the water-cooled 996 engines are really very different. For example, the 996 runs best with a 210 deg F water temps and a 210-220 oil temperature. Compare that to a 993 that runs best at 190-200 deg oil temp. If you read about the 996's VarioCam operation, you will soon see that making general oil viscosity recommendations is tough, since their operating environmens are not the same.
Chip (above) offered some true pearls of wisdom about basic oil chemistry. Although its nice to read about very-wide viscosity oils that appear to be all things for all people, reality is different and looking inside engines is the ultimate proof,....
As Chip said, those 0w-40 and 5w-50 oils are comprised of many long chain molecules that are temperature stable, up to a point. With the water-cooled engine's better control of oil temps (it shares the cooling load with water/antifreeze), those oils hold up better and longer before they begin breaking down toward their base stocks.
As I stated back in Feb, 911 air-cooled engines see greater peak temps than what you see on the gauge which after all, is only sampled at one point in the engine. For that reason and others, 993 motors do better in hot climates (and at the track) if a 15w-50 is used. The criteria here is wear & tear.
There is no question that thinner oils lubricate faster on startup and provide better fuel economy so Porsche's recommendation reflect those requirements.
As Edward said, the Factory oil recommendations (and others) are not all that altruistic so one really should contact experienced engine builders to find out the Big Picture,....
Its been fun reviewing this thread since its started back in February.
IMHO, a clarification might be needed here. The operating conditions inside the air-cooled 993 engines and the water-cooled 996 engines are really very different. For example, the 996 runs best with a 210 deg F water temps and a 210-220 oil temperature. Compare that to a 993 that runs best at 190-200 deg oil temp. If you read about the 996's VarioCam operation, you will soon see that making general oil viscosity recommendations is tough, since their operating environmens are not the same.
Chip (above) offered some true pearls of wisdom about basic oil chemistry. Although its nice to read about very-wide viscosity oils that appear to be all things for all people, reality is different and looking inside engines is the ultimate proof,....
As Chip said, those 0w-40 and 5w-50 oils are comprised of many long chain molecules that are temperature stable, up to a point. With the water-cooled engine's better control of oil temps (it shares the cooling load with water/antifreeze), those oils hold up better and longer before they begin breaking down toward their base stocks.
As I stated back in Feb, 911 air-cooled engines see greater peak temps than what you see on the gauge which after all, is only sampled at one point in the engine. For that reason and others, 993 motors do better in hot climates (and at the track) if a 15w-50 is used. The criteria here is wear & tear.
There is no question that thinner oils lubricate faster on startup and provide better fuel economy so Porsche's recommendation reflect those requirements.
As Edward said, the Factory oil recommendations (and others) are not all that altruistic so one really should contact experienced engine builders to find out the Big Picture,....
08-28-2004, 05:48 AM
#19
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Wow, I never realised something so potentially simple could actually be so complex !!!!!! As a driver of a 996 C4 - never tracked but hard road driving occasionally - who lives in the rather warm climate of soutern Spain, am I right in assuming from reading all the input above (thanks all you experts) that my 996 is ok with 0w-40 ??? only one problem here is that I can´t get Mobil !!!!
08-28-2004, 10:09 AM
#21
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Okay, last question. What about those of us who don't see track time? Unless the region's rules change (figure the odds) or I break down and decide to make the back seats unusable for my little ones (another long shot) my garage queen gets used for commuting, weekend fun, and the occasional spirited drive in the country. Informal viewing of the temp guage makes it appear that max temps are experienced stuck in stop and go traffic on the way home. 
Should I still go with the higher weight, or since my engine may not be experiencing the same extremes would the 0-40 be appropriate here?
btw, I'm planning to replace my lower valve cover gaskets and do my annual oil change Labor Day weekend so this comes at exactly the right time.
Should I still go with the higher weight, or since my engine may not be experiencing the same extremes would the 0-40 be appropriate here? btw, I'm planning to replace my lower valve cover gaskets and do my annual oil change Labor Day weekend so this comes at exactly the right time.
08-28-2004, 11:13 AM
#22
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solsrch -
I would say that for the conditions under which you drive your car, the 0W-40 is the right selection. Your engine doesn't spend a lot of time at high rpm so the oil should hold up fine. Though it does get hot in stop and go driving, it still doesn't see the localized extreme high temperatures that a hard run engine will present. Since the 0W-40 flows to engine parts that need oil more quickly at startup than 15W-50, and engine wear will actually be lower with thinner oil (as long as you don't actually reach the heat/load that causes viscosity breakdown of the thinner oil, and I doubt you do) the 15W-50 probably offers no advantage and perhaps a theoretical disadvantage. Still, many experts will recommend the 15W-50, since it is the safest choice if there is any question.
If you wanted to be especially careful, you could change the 0W-40 oil out more frequently than Porsche recommends (say every 3000-6000 miles), keeping its benefits while avoiding its potential 'weaknesses'. My own practice is to start off the year in the spring with fresh 15W-50. After the last DE and hot weather for the year, I'll suck out several quarts and replace those quarts with 0W-30 Mobil1. The net result is close to a 10W-40 for the winter. It sounds a bit ****, but its easy to do.
If you want to be really compulsive, send off a sample of the oil at oil change for an oil analysis, that can tell you if the oil is beginning to break down, and additionally warn you about unusual levels of wear metals and other things in the oil. Its easy and cheap, at about $20 a pop. I've used several analysis services myself, currently using Blackstone Laboratories ( http://www.blackstone-labs.com/ ) but there are many other good ones out there.
Chip
I would say that for the conditions under which you drive your car, the 0W-40 is the right selection. Your engine doesn't spend a lot of time at high rpm so the oil should hold up fine. Though it does get hot in stop and go driving, it still doesn't see the localized extreme high temperatures that a hard run engine will present. Since the 0W-40 flows to engine parts that need oil more quickly at startup than 15W-50, and engine wear will actually be lower with thinner oil (as long as you don't actually reach the heat/load that causes viscosity breakdown of the thinner oil, and I doubt you do) the 15W-50 probably offers no advantage and perhaps a theoretical disadvantage. Still, many experts will recommend the 15W-50, since it is the safest choice if there is any question.
If you wanted to be especially careful, you could change the 0W-40 oil out more frequently than Porsche recommends (say every 3000-6000 miles), keeping its benefits while avoiding its potential 'weaknesses'. My own practice is to start off the year in the spring with fresh 15W-50. After the last DE and hot weather for the year, I'll suck out several quarts and replace those quarts with 0W-30 Mobil1. The net result is close to a 10W-40 for the winter. It sounds a bit ****, but its easy to do.
If you want to be really compulsive, send off a sample of the oil at oil change for an oil analysis, that can tell you if the oil is beginning to break down, and additionally warn you about unusual levels of wear metals and other things in the oil. Its easy and cheap, at about $20 a pop. I've used several analysis services myself, currently using Blackstone Laboratories ( http://www.blackstone-labs.com/ ) but there are many other good ones out there.
Chip
Last edited by 914und993; 08-28-2004 at 11:32 AM.
08-28-2004, 02:39 PM
#24
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15-50 Mobil One is my oil-of-choice. 113k miles and doing great! 
I live in sunny northern california, so temps are moderate - never "Arizona" hot or "Minnesota" cold...
I live in sunny northern california, so temps are moderate - never "Arizona" hot or "Minnesota" cold...
