I was perusing spec sheets from RedLine, Mobil, Shell, and Amsoil last night and I noticed something that confused me. It looked to me like in almost or perhaps all cases the 40C kinematic viscosity of the 5W-40 oils was higher than that of the 10W-30 oils. Why in the world is that?
5W-40 thicker than 10W-30 at 40C?
- Thread starter bulwnkl
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Because 40 is heaver than 30 weight at 40 degrees C.
Nice thread, thanks. I tried a couple of searches, but didn't turn that one up. It would seem that, although I knew things about the Winter number versus the the "regular" number, I lacked sufficient understanding of what I knew.
Between the other thread and the viscosity chart, one might be inclined to infer that there is no operational difference whatsoever between a 0W-30, 5W-30, and 10W-30 if a person lives in a place where the oil never drops below, say -10C. Is that a reasonable inference?
--E
[ February 16, 2005, 11:37 AM: Message edited by: bulwnkl ]
Between the other thread and the viscosity chart, one might be inclined to infer that there is no operational difference whatsoever between a 0W-30, 5W-30, and 10W-30 if a person lives in a place where the oil never drops below, say -10C. Is that a reasonable inference?
--E
[ February 16, 2005, 11:37 AM: Message edited by: bulwnkl ]
..... With high Summer ambient 90+ then I would look at the HT/HS of these oils. [/QB][/QUOTE]
...so are you saying that the HTHS value is "less" of a concern during winter use? [/QB][/QUOTE]
No, but higher ambient and load conditions make it more of a factor. Pick the right 0W-30 and have the best of both worlds. XD-3 and GC work well for most of us. Even in Winter heavy hauling would be a factor.
Some people think that oil should be thicker at start-up. I have never seen evidence to support this in my 35 years of oil studies. There are however numerous studies to the contrary. At 50 F the 0W-20 Mobil 1 has a viscosity of 189, at zero F it is about 750. While these may have some flow they do not lubricate well and if one steps on the gas cavitation and oil starvation is certain to occur. Even with today's oils with less thickening on engine shut-down car manuals are stating to keep the RPM down until fully warmed. Putting in a 50 or 60 wt oil having viscosities in the 20 - 25 cS range (at full operating temperature) is still too high for most engines. Certainly 189 cS at any temperature is detrimental. I feel that 189 cS cannot be considered to be too thin for any automotive condition or purpose.
More and more oil recommendations make no mention of ambient temperature conditions. If the oil is a 0 or 5W-XX formulation then it will work in cold conditions and there is only the benefit at summer temperatures of still being less thick at start-up.
While many cars have some sort of oil pressure gauge, few have oil temperature gauges. I think you will find that oil temperatures do not vary with ambient temperatures. I say this from quoting articles and from personal experience of numerous sports cars I owned living from NJ, NC and now FL.
aehaas
More and more oil recommendations make no mention of ambient temperature conditions. If the oil is a 0 or 5W-XX formulation then it will work in cold conditions and there is only the benefit at summer temperatures of still being less thick at start-up.
While many cars have some sort of oil pressure gauge, few have oil temperature gauges. I think you will find that oil temperatures do not vary with ambient temperatures. I say this from quoting articles and from personal experience of numerous sports cars I owned living from NJ, NC and now FL.
aehaas
AEHaas would you not generally agree though that 0W-5W-10W ratings can be somewhat misleading to the consumer. CCS and MRV # plus seat of the pants have shown me that all is not equal here. Some of it is marketing perhaps? If I can't sell 0W-20 to Ford and Honda owners, can't I just call it 5W-20 where it sells?? I've seen some very good 10W-30 syns that flow extremely well at moderate temps.
I'm not convinced that at 50F or 60F there is a significant wear difference between any of the xW-30's based on viscosity alone.
Pushrods are more forgiving, but perhaps with the modern DOHC and multi-valve designs that thinner is more significant, but the additive packages seems to be more important as well.
I'm not convinced that at 50F or 60F there is a significant wear difference between any of the xW-30's based on viscosity alone.
Pushrods are more forgiving, but perhaps with the modern DOHC and multi-valve designs that thinner is more significant, but the additive packages seems to be more important as well.
I fully agree. We need to look at actual numbers, not the label on that jar of oil. Yes, they are misleading.
The J300 was changed to make currently labeled 10W-30 weight oil meet what was in 1990 the 5W-30 standard. Even the API and SAE are trying to make us use oils that thicken less after engine shut-down.
aehaas
I believe that 10W-30, 15W-40 and 20W-50 motor oils for gasoline SI engines exist only for those who are not keeping up with oil technologies, again, marketing. Newer automotive manuals are not calling for these oils but rarely.
[ February 16, 2005, 02:03 PM: Message edited by: AEHaas ]
The J300 was changed to make currently labeled 10W-30 weight oil meet what was in 1990 the 5W-30 standard. Even the API and SAE are trying to make us use oils that thicken less after engine shut-down.
aehaas
I believe that 10W-30, 15W-40 and 20W-50 motor oils for gasoline SI engines exist only for those who are not keeping up with oil technologies, again, marketing. Newer automotive manuals are not calling for these oils but rarely.
[ February 16, 2005, 02:03 PM: Message edited by: AEHaas ]
I think RPM is a key factor.
It's 31 degress F outside, I'm heading out to work, the Citgo 10W-30 GRP III syn I'm running in my Silverado 5.3L is 570 cSt at this temperature.
This truck will cold start idle at 900 rpm and based on the shift points of the automatic transmission, won't see over 2300 rpm till it gets out on the highway and will settle in at 1700 rpm (overdrive) at 60mi/hr.
I don't view this oil at 600 centistokes, as being too thick of a viscosity, or generating excessive wear at start-up.
You mean they vary more like ground temperatures do compared to ambient air? That is: they DO vary with ambient temperatures, but they lag behind significantly.
If so I certainly agree. Plus, oil in the pan has a big heat soak right above it for quite a while which significantly slows cooldown. It might seem, though, that this would tend to reduce the need for very low Winter ratings. The oil temp in a "cold" engine (one that has not run for 4 hours) is likely to be far above ambient air temp. I'm not saying lower Winter grades are not desirable or even necessary, just that the above factors would tend to reduce any such necessity.
Patman
Staff member
What are you going to use once the supply of M1 0w20 dries up? (Mobil 1 is only going to make 5w20 now, they've discontinued the 0w20)
Who else makes a 0w20 oil?
0W-20 is just a label. I will be studying all the actual numbers as they become available. For now I have a stash of 0W-20 and 30 M1.
aehaas
aehaas
What you pointed out is very important to me. People often look only at the pre-W number as if it’s only importance is in the winter in Canada. I live in Florida and I always look for the oil with 0W-XX and the lowest pour point.
The reason is that at 50 or 60 F these oils are easier on your engine at start-up. For example, a Mobil One 0W-20 has a viscosity of 189 at 50 F. A typical 10W-30 mineral oil would have a viscosity of 400 at that temperature. They may have similar thicknesses at operation but huge differences at start-up even here in Florida. Since the start-up period is where most wear occurs this should be considered. Few pay any attention to this most important issue. The whole purpose of the development of multi-grade oils is to minimize start-up wear, not to be able to start you car in Antarctica.
Any car using a 40 wt synthetic can be started in sub-zero temperatures and most cars with 40 wt dino oils may be started also but the aim is a total reduction in start-up wear with oils that thicken less on engine shut-down.
I have been preaching for years that we should pick oils with the appropriate operating viscosity, be it a 20, 30 or 40 wt oil, but then select the lowest “W” number and pour point as possible. This way you get the operating viscosity you want while minimizing start-up wear.
You may benefit from reading my chapters under the Interesting Articles section.
aehaas
The reason is that at 50 or 60 F these oils are easier on your engine at start-up. For example, a Mobil One 0W-20 has a viscosity of 189 at 50 F. A typical 10W-30 mineral oil would have a viscosity of 400 at that temperature. They may have similar thicknesses at operation but huge differences at start-up even here in Florida. Since the start-up period is where most wear occurs this should be considered. Few pay any attention to this most important issue. The whole purpose of the development of multi-grade oils is to minimize start-up wear, not to be able to start you car in Antarctica.
Any car using a 40 wt synthetic can be started in sub-zero temperatures and most cars with 40 wt dino oils may be started also but the aim is a total reduction in start-up wear with oils that thicken less on engine shut-down.
I have been preaching for years that we should pick oils with the appropriate operating viscosity, be it a 20, 30 or 40 wt oil, but then select the lowest “W” number and pour point as possible. This way you get the operating viscosity you want while minimizing start-up wear.
You may benefit from reading my chapters under the Interesting Articles section.
aehaas
JHZR2
Staff member
I agree with you for the most part, but inbetween viscosities must be matched to the requirements of the tolerances in the engine when the metal is cold, the output of the oil pump, the typical rpms seen, etc.
This is why in most areas, a viscosity chart is given to determine operation at what range of max ambient temperatures. this way lubrication can be tailored to the engine much more than usual.
It certainly is agreed that fast flow of oil is important. But it seems to me that in some situations, it is not enough, as if a fast flowing, but too thin layer is produced, it may not provide adequate protection, especially at transient operation wen very cold.
I think many syn oils, newer engine designs, etc have solved this somewhat. And weve seen lots of good UOAs, from all sorts of different oil uses, temperatures, etc. But it seems that there is always some tailoring to be done.
JMH
This is why in most areas, a viscosity chart is given to determine operation at what range of max ambient temperatures. this way lubrication can be tailored to the engine much more than usual.
It certainly is agreed that fast flow of oil is important. But it seems to me that in some situations, it is not enough, as if a fast flowing, but too thin layer is produced, it may not provide adequate protection, especially at transient operation wen very cold.
I think many syn oils, newer engine designs, etc have solved this somewhat. And weve seen lots of good UOAs, from all sorts of different oil uses, temperatures, etc. But it seems that there is always some tailoring to be done.
JMH
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