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Discussion Starter #1
I searched but could not find the thread where Saabhoemme gave some info on why 5-W-30 may actually be better than 0W-40. Something about the differential between low and high number. I have exclusively used 0W-40 and all seemed good. Recently tho I had a stuck lifer it seems and some sludge in my tuned 2011 Turbo4. I always felt 0W was better for a Turbo on startup and 40W was better in my Arizona summer temps. 100-115 for months

Saabhoemme, refresh my memory, please
 

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The basic gist of that premise is that the VI differential is created by modifying the base stock with viscosity modifiers. The wider the differential, the more modifiers needed to change the inherent characteristics of the base stock, to make it behave like a less viscous fluid when cold and a more viscous fluid when hot. Stated more appropriately, the VI modifiers are added to abate the natural tendency of the oil to become less viscous when hot.

VI modifiers are long chain polymers that contract in the presence of cold and expand in the presence of heat, like most solids do. Their impact on a fluid (motor oil for our purposes) is minimal at cold temperatures, so to make a 0W oil, the manufacturer must begin with extremely thin base stock. To get 0W40, it must add quite a bit of these modifiers to make the base oil increase in viscosity to meet the industry specs required of a 40 weight oil as temperature rises.

The base stock and the long chain polymers are susceptible to shear down, so during the service life of the oil, it will naturally begin to thin down. We have all heard or read complaints about Mobil 1 0W40 being on the thin side for 40 weight to begin with. As it ages, as it is used, at some point in its service life it essentially becomes more of an 0W30 oil than an 0W40 oil.

But viscosity alone is not the be-all end-all of how oil lubricates and protects. We also need to be concerned with film strength. Now if we have an 0W40 and an 0w30 motor oil that have the same film strength at startup temperature, the 0W40 may give a little more headroom for protection from wear (at the cost of slightly higher fuel consumption due to increased internal friction) at operating temperature, for the reason that it is more likely to have a little higher viscosity rating at that temperature and this higher viscosity may assist in protecting the moving metal parts as film strength begins to get taxed.

But so long as the film strength of the oil remains adequate throughout the operating range of the oil, meaning that it remains capable of keeping metal surfaces from grinding away on each other, then increased viscosity by itself does not do all that much, if anything, other than robbing you of power and efficiency.

In this way, motor oil chemistry is quite illustrative of the phenomenon first articulated by our dear friend Sir Isaac Newton: for every action there is an opposite and equal reaction. Hot-rodders have learned this by shared common experience. Every thing we do has intended (usually good) consequences, accompanied by unintended (usually bad) consequences. Want a cheap and easy way to increase low end torque for improved take off? Increase the length of the intake runners to increase air mass velocity. But uh, then we lose top end power. Want a cheap way to increase air flow into the combustion chamber and make more power? Pull the head and hog it out as much as you can and slap it back on. Great, we just a made a dyno queen that makes 100 more horsepower than stock, but only at redline.

This same basic principle applies to making a good motor oil. We can do one thing exceptionally well, but almost always at the expense of another thing or things. The trick is achieving a balance that serves the intended use, and thus the goal is to create a lubricant that meets the real world needs of drivers everywhere.

Since a great amount of mechanical wear occurs to most, if not all, automobile engines at start-up after the vehicle has been sitting overnight, and since lubricant flow is the most important lubricant characteristic to combat this wear on start-up, manufacturers developed these 0W oils, where the 0W designation indicates low viscosity when cold (and remember, viscosity represents resistance to flow). To make them usable for us, they had to find a way to make their products resist the natural tendency to thin down even further. Hence the VI modifiers. And hence as well, and equally importantly, the continued R&D into increasing base oil film strength.

All other things being equal, 0W oils will give the majority of drivers the best protection year round if for no other reason than that these oils will provide the best start-up protection. For you, living in Southern AZ, I doubt that changing to a 5W oil will hurt you on startup. Your main concern is to maintain protection at operating temperature since your ambient temps regularly exceed 100 deg F. Included in that is the need to maintain oil pressure during normal driving cycles, which includes idling, when oil pressure will drop to its lowest point.

Here is where viscosity itself becomes the critical factor. Viscosity resists flow, but at operating temperature flow should already be well established and a not an issue. Increased fluid viscosity also equates with increased fluid pressure in a closed system. So at operating temperature, with all other things being equal, it is fluid viscosity that becomes the most important variable for oil pressure.

When I say "all other things being equal" I mean I am assuming your lubrication system is in good operating condition, i.e. the oil pump is within spec and there are no major leaks or obstructions within the system. If all that is true and you regularly have minimal oil pressure at some point or points during your daily driving, increasing operating temperature viscosity will help increase the oil pressure. Changing to a 5W oil from an 0W oil may be of some help for the foregoing reasons, since the base stock of a 5W will be more viscous to begin with than that of an 0W. But of course, increasing the second oil viscosity rating number (the 20 or 30 or 40 or 50) should have an even bigger impact on final operating temperature viscosity.

Finally, you mentioned sludge or crud causing a lifter to stick. Varnish build up is a well known cause for sticking lifters, as is low oil pressure. We have just discussed oil pressure.

To combat varnish and sludge, oils have detergents. But like anything, they don't last forever, nor do oil filters. Which is why, notwithstanding the industry stampede to extended service intervals, I continue to change my oil every 5,000 miles or annually, whichever comes first. Because I am a Luddite and dinosaur. When I die, I want to be made into motor oil. Unless I die due to spontaneous human combustion, to become mere air pollution.
 

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The basic gist of that premise is that the VI differential is created by modifying the base stock with viscosity modifiers. The wider the differential, the more modifiers needed to change the inherent characteristics of the base stock, to make it behave like a less viscous fluid when cold and a more viscous fluid when hot. Stated more appropriately, the VI modifiers are added to abate the natural tendency of the oil to become less viscous when hot.

VI modifiers are long chain polymers that contract in the presence of cold and expand in the presence of heat, like most solids do. Their impact on a fluid (motor oil for our purposes) is minimal at cold temperatures, so to make a 0W oil, the manufacturer must begin with extremely thin base stock. To get 0W40, it must add quite a bit of these modifiers to make the base oil increase in viscosity to meet the industry specs required of a 40 weight oil as temperature rises.

The base stock and the long chain polymers are susceptible to shear down, so during the service life of the oil, it will naturally begin to thin down. We have all heard or read complaints about Mobil 1 0W40 being on the thin side for 40 weight to begin with. As it ages, as it is used, at some point in its service life it essentially becomes more of an 0W30 oil than an 0W40 oil.

But viscosity alone is not the be-all end-all of how oil lubricates and protects. We also need to be concerned with film strength. Now if we have an 0W40 and an 0w30 motor oil that have the same film strength at startup temperature, the 0W40 may give a little more headroom for protection from wear (at the cost of slightly higher fuel consumption due to increased internal friction) at operating temperature, for the reason that it is more likely to have a little higher viscosity rating at that temperature and this higher viscosity may assist in protecting the moving metal parts as film strength begins to get taxed.

But so long as the film strength of the oil remains adequate throughout the operating range of the oil, meaning that it remains capable of keeping metal surfaces from grinding away on each other, then increased viscosity by itself does not do all that much, if anything, other than robbing you of power and efficiency.

In this way, motor oil chemistry is quite illustrative of the phenomenon first articulated by our dear friend Sir Isaac Newton: for every action there is an opposite and equal reaction. Hot-rodders have learned this by shared common experience. Every thing we do has intended (usually good) consequences, accompanied by unintended (usually bad) consequences. Want a cheap and easy way to increase low end torque for improved take off? Increase the length of the intake runners to increase air mass velocity. But uh, then we lose top end power. Want a cheap way to increase air flow into the combustion chamber and make more power? Pull the head and hog it out as much as you can and slap it back on. Great, we just a made a dyno queen that makes 100 more horsepower than stock, but only at redline.

This same basic principle applies to making a good motor oil. We can do one thing exceptionally well, but almost always at the expense of another thing or things. The trick is achieving a balance that serves the intended use, and thus the goal is to create a lubricant that meets the real world needs of drivers everywhere.

Since a great amount of mechanical wear occurs to most, if not all, automobile engines at start-up after the vehicle has been sitting overnight, and since lubricant flow is the most important lubricant characteristic to combat this wear on start-up, manufacturers developed these 0W oils, where the 0W designation indicates low viscosity when cold (and remember, viscosity represents resistance to flow). To make them usable for us, they had to find a way to make their products resist the natural tendency to thin down even further. Hence the VI modifiers. And hence as well, and equally importantly, the continued R&D into increasing base oil film strength.

All other things being equal, 0W oils will give the majority of drivers the best protection year round if for no other reason than that these oils will provide the best start-up protection. For you, living in Southern AZ, I doubt that changing to a 5W oil will hurt you on startup. Your main concern is to maintain protection at operating temperature since your ambient temps regularly exceed 100 deg F. Included in that is the need to maintain oil pressure during normal driving cycles, which includes idling, when oil pressure will drop to its lowest point.

Here is where viscosity itself becomes the critical factor. Viscosity resists flow, but at operating temperature flow should already be well established and a not an issue. Increased fluid viscosity also equates with increased fluid pressure in a closed system. So at operating temperature, with all other things being equal, it is fluid viscosity that becomes the most important variable for oil pressure.

When I say "all other things being equal" I mean I am assuming your lubrication system is in good operating condition, i.e. the oil pump is within spec and there are no major leaks or obstructions within the system. If all that is true and you regularly have minimal oil pressure at some point or points during your daily driving, increasing operating temperature viscosity will help increase the oil pressure. Changing to a 5W oil from an 0W oil may be of some help for the foregoing reasons, since the base stock of a 5W will be more viscous to begin with than that of an 0W. But of course, increasing the second oil viscosity rating number (the 20 or 30 or 40 or 50) should have an even bigger impact on final operating temperature viscosity.

Finally, you mentioned sludge or crud causing a lifter to stick. Varnish build up is a well known cause for sticking lifters, as is low oil pressure. We have just discussed oil pressure.

To combat varnish and sludge, oils have detergents. But like anything, they don't last forever, nor do oil filters. Which is why, notwithstanding the industry stampede to extended service intervals, I continue to change my oil every 5,000 miles or annually, whichever comes first. Because I am a Luddite and dinosaur. When I die, I want to be made into motor oil. Unless I die due to spontaneous human combustion, to become mere air pollution.
Which of these two (5W-30 and 0W-40) would you recommend for weather temperature at 90-100 deg F all year round?
 

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Not a simple question.
Both and either. Assuming both do what is required to lubricate and protect the engine at all times.

When I started driving, there were still straight weight motor oils in use in cars and trucks. Not long after came 10W30 and then 10W40, which for years were the leaders of automobile multi-vis oils. We used these oils with confidence in temperate climes.

Cars are designed entirely differently today. They are designed to run a little hotter for efficiency reasons. They make more power using less fuel and are designed to run right up to the onset of knock. Some of them are designed with such tight tolerances that the manufacturer insists that you use an XW20 weight oil (although some of that insistence is to meet CAFE requirements), regardless of geography.

A good 10W40 oil will never suffice in an engine that has super tight tolerances. Otherwise, it still works in most cars. But trade-off time again, it will never, not even at the equator, flow as fast on start up as any good 0W or 5W oil will. (Whether that will make an appreciable difference in the healthy longevity of an engine in the real world may remain open for debate). On the other hand, it will maintain its operating temperature viscosity longer and more easily and help a little with maintaining oil pressure at idling on super hot days, where the 0W30, 0W40 and 5W30 and 5W40 may struggle a tiny bit more to do so.
All this is all theoretical limit stuff.

The final test is whether the oil works in your car where you live how you use it (which includes how rigorously or lackadaisically you service it). If you do semi-regular oil analyses when you start using an oil, you have some quantitative objective evidence that it does or does not, right near the beginning. Or if you start using an oil and continue to do so and put 250,000 miles on the engine and it is still going strong when the car is otherwise all worn out or becoming too expensive to maintain because all the electronic geewhiz gizmos are failing and the A/C is verklempt and the trans is acting up, then you have after the fact empirical evidence that that oil was adequate unto your needs. If you are into the fifth or seventh year of ownership with no oil analysis, and have experienced no lubrication issues like low oil pressure warnings, sludging, nasty noises, unusual reductions in fuel mileage, and/or smoke from the tailpipe or under the hood, then you are prolly OK.
If it were I, I suppose I would consider a quality 5W40 or 5W30 oil for daily use, assuming morning temperatures rarely dropped below 50 deg F or so. Obviously, low altitude desert should be just fine. High altitude desert, like near Flagstaff, maybe not as much. In the latter case, I would still try for an 0W something that fits the bill.
 

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Discussion Starter #5
Great stuff, but still not sure how to avoid any sludge problems, or stuck lifters.
I change oil twice a year, average of 3,500 miles. Always 0W-40.
0W-40 in "winter" in Arizona and 5W-30 in summer may be the best strategy.

As much as I don't believe in chemical fixes it worked this time. I may just do a cleaner every year or two and a lifter lube for at least one oil change a year.
 

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It's not like there's a single 0W-40 or 5W-30.


I once put Mobil 1 0W40 in my 1997 NG900 (B234i), and I got the low oil bing-bong if I goofed the clutch and dropped the revs too low a few times....and this was in the middle of winter (Canadian winter, you know, frozen white water and everything). But this never happened with Castrol Syntec/Edge 0W-40.


I can't see any difference between Mobil or Castrol 0W-40 in by B235 9-5. I have way more jugs of the Castrol, because it comes in 5L sizes, goes on sale often, and Castrol Canada's facilities are a ten minute walk away so I'm kind of supporting local.


To the case of the sticking lifter, there are some other causes I would ascribe it to, before accusing the oil. The oil filter used, the oil filter change frequency, and the driving conditions (desert dust?) could affect how clean the oil was. It could also be a mechanical fault, or a characteristic of your particular engine.


I suspect that playing around with the exact oil brand or weight, or using some additive, won't make any difference. The sound may go away, in which case it was going to go away in any case. It may continue, at which point you have to decide if you can live with the noise and worry about potential damage. Or it could get worse, in which case there's head work coming up.
 

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Discussion Starter #7 (Edited)
You raise some valid points but always Mobil 1 0W-40, twice a year, about 4000 miles.

Filters? SAAB OEM, Mann, Wix XP, or similar. No Fram or WalMart.

Two other 9-3 also fed the same diet with no issues, 80,000 mile V6, 150,000 mile 2.0 T.

But I do not know if previous owner pushed the car. He also used Mobil 1 tho.
Will keep an eye on it and report back periodically. For all my posts I did not get one reply from someone with similar issue

Surprisingly few issues with dust being picked up on my other two, they have OEM air intake. This one has a BSR CAI with an AEM filter. Not a fan as ain't nothing cold air about it, it pulls from under the hood. Whereas stock pulls from beneath the engine. Came this way to me 2 1/2 years ago, thinking of going back to stock.
 

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The Old oil dilemna... The lower value the machine.. the more 'important' the oil choice becomes.
I use 15/40 Delvac since '84 in my saabs.
It works Fine.. thank you.
I don't live in sub arctic climes so I don't need low viscosity pour when frozen qualities Also prefer oil that works when hot...
OR, the lotsa STP (thickening Polymer) that a high weight range oil must contain.... displacing the actual LUBE oil content of the soup mix.
There is only so much room in an oil can :)
 

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I can only speak to the oil analysis' that keeps coming back on one of my 9-3 SS's. 0w40 Mobil 1 is an excellent oil for the 2.0t from what those oil analysis are telling me. The 03 I have has 225K miles and comes back with analysis that looks like oil from a motor with 1/4 of those miles! Both in the hot summers and the brutally cold winters.
 

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I run M1 0W40 euro formula on all 3 of our 2.0T cars. Get it at WalMart. At ~$12/5L after MIR that happens a few times a year my oil changes are super cheap.
 

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I've been running 0W-40 Mobil 1 in my 2000 and 2001 9-5 Aeros, but last night I switched the 2000, which has 215,000 miles, to 5W-40 Mobil 1 turbo diesel truck oil. The engine was noticeably smoother on the drive to work, and sounded quite a bit less harsh. The 2001 had its engine rebuilt recently with all new rings and bearings, and sounds very smooth as-is, so I'll stick with 0W-40 in that car since it's as new as it's going to get. The 2000 burns quite a bit of oil, so hopefully a slightly heavier oil will help with that, at least a tiny bit.
 
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