My Hat's off to Doug
01-25-2005, 06:30 PM
#16
01-25-2005, 06:50 PM
#17
Instructor
Thread Starter
Let me please clarify the HTHS cST numbers I was misquoted for. RedLine's 5/40 is 4.6. RedLine's 20/50 is 6.1. I don't know of the numbers for Amsoil's, but I do know that M1/s 15/50 is 5.3. That being said...yes these higher quality oils actually can give you the flow, power conservation, lower temperature, and bearing protection of the lower number, while at the same time provide the viscosity protection during extreme heat and stress. Dino oils just can't do it, and not all synthetics are created equal.
Best wishes to all...don't mean to beat a dying horse. I just think that these technologies were not available at the time this car came out, but if the protection is there, why not use a very good oil. It's not like our cars are cheap or that motor repair is affordable. The difference between an 'exotic' oil and an everyday is only about $50 per change ($2qt. versus $8qt).
Best wishes to all...don't mean to beat a dying horse. I just think that these technologies were not available at the time this car came out, but if the protection is there, why not use a very good oil. It's not like our cars are cheap or that motor repair is affordable. The difference between an 'exotic' oil and an everyday is only about $50 per change ($2qt. versus $8qt).
01-25-2005, 07:46 PM
#18
Rennlist Member
That's like saying General Mills, the leading money making food supplier, makes the heathiest cereals.
One could also say, you get what you pay for (i hope!!).......
I understand everyones points, and certainly i have limited knowledge in the area of oils, other than , my own personal feelings/preference. I also have more hard driven miles than most and have taken apart an engine with only me driving it racing and street for over 170,000+miles using these more expensive brands. Ive also never overheated my engines, and never had redline or pinging issues. maybe if i had Mobil1 in the car the results would have been the same. I dont know. but, what i do know, is that when i had the mobil 1 on the race track, the pressure was noticibly lower, and dramatically lower when hot. may not be an issue for day to day street driving, but i bet it is on the race track. (again, a guess on my part)
Mk
One could also say, you get what you pay for (i hope!!).......
I understand everyones points, and certainly i have limited knowledge in the area of oils, other than , my own personal feelings/preference. I also have more hard driven miles than most and have taken apart an engine with only me driving it racing and street for over 170,000+miles using these more expensive brands. Ive also never overheated my engines, and never had redline or pinging issues. maybe if i had Mobil1 in the car the results would have been the same. I dont know. but, what i do know, is that when i had the mobil 1 on the race track, the pressure was noticibly lower, and dramatically lower when hot. may not be an issue for day to day street driving, but i bet it is on the race track. (again, a guess on my part)
Mk
Originally Posted by BrendanC
I think you also have to add in the starts and stops the engine has to go through as a daily driver. That needs a thinner, easier flowing oil. I wish there was a BIT thinner oil from Amsoil.
But Doug did mention that Mobile one has had many more millions of dollars invested in thier technology then Amsoil or Redline could ever invest. Does this mean that there is a better chance of having more technology actually put into the product? I have no idea. One would hope.
Maybe because EVERYONE uses Mobil1 there are more engines lost, and since only a few individuals race 928s with Amsoil, there have been no failures?
I took apart my 928S4 engine, and there was considerable polishing of the mains and rod bearings. I had amsoil in it from 37k to 75k. Very hard driving at all times. Many redline bouncing brain-farts.
But Doug did mention that Mobile one has had many more millions of dollars invested in thier technology then Amsoil or Redline could ever invest. Does this mean that there is a better chance of having more technology actually put into the product? I have no idea. One would hope.
Maybe because EVERYONE uses Mobil1 there are more engines lost, and since only a few individuals race 928s with Amsoil, there have been no failures?
I took apart my 928S4 engine, and there was considerable polishing of the mains and rod bearings. I had amsoil in it from 37k to 75k. Very hard driving at all times. Many redline bouncing brain-farts.
01-25-2005, 07:53 PM
#19
Rennlist Member
so far, ive only been using about a quart of oil per race weekend, and hardly any between weekends (roughly 1-2k miles)
Now, as far as temps are concerned, im running close to 260 oil temps on the hottest days at the track. normally, on a hot day, its 200 to 225 under street sport conditions on a hot day. cruising, around 180. this is oil temp, which i suppose you are refering too. 225 is pretty warm and i imagine if you do get full throtle and these temps often, it would be worth 20-50 weight oils. If not, as say i do with my BMW street car, 10-40, 5-30 would be fine.
(more guesses)
MK
Now, as far as temps are concerned, im running close to 260 oil temps on the hottest days at the track. normally, on a hot day, its 200 to 225 under street sport conditions on a hot day. cruising, around 180. this is oil temp, which i suppose you are refering too. 225 is pretty warm and i imagine if you do get full throtle and these temps often, it would be worth 20-50 weight oils. If not, as say i do with my BMW street car, 10-40, 5-30 would be fine.
(more guesses)
MK
Originally Posted by wino5150
The other components of oil that seem to matter are the pour point, flash point, and also very important the degree or percentage of evaporation/destruction (very high for M1...very low for Amsoil and Redline...like the difference between 11% and 6%...talk about oil consumption)
So...make up your own mind and in the end, these engines are designed with large volumes in the oil compartment...so probably won't matter. Will 5W be enough to protect during track temps...has a higher flash point, HTHS value, and offers better flow to the bearings...we'll see.
Best wishes to all...as a note, 20/50 is not recommended in engines seeing temperatures less than 225...I believe mine runs around 190 to 210 even going full throttle.
So...make up your own mind and in the end, these engines are designed with large volumes in the oil compartment...so probably won't matter. Will 5W be enough to protect during track temps...has a higher flash point, HTHS value, and offers better flow to the bearings...we'll see.
Best wishes to all...as a note, 20/50 is not recommended in engines seeing temperatures less than 225...I believe mine runs around 190 to 210 even going full throttle.
01-26-2005, 01:38 AM
#20
Shameful Thread Killer
Rennlist Member
Rennlist Member
A few things to note about oil viscosity. The newer low viscosity oils were developed by oil companies at the behest of many auto mfg companies. As has been said, lower viscosity oils have a lower shear, and generally lower resistance to flow, and are 'more slippery'(sorry for being simple). The lowering of viscosity helped car makers meet both fuel economy numbers and emission standards. I have a pre-war car, and wouldn't ever consider using a modern low-vis multi grade oil in it. While a 20-50 is too thick for modern engines with their very close tolerances, the oposite is true on older engines. I think the 928 is probably somewhere between the pre-war thick stuff, and the modern super low vis stuff.
Now, as to pressure. The best pressure for an engine, is one that will provide complete surface coverage of bearings, at all temps, and RPM, with the least pressure. The pressure is only there to force the lubricant into the journal. Any extra pressure wastes energy, increases temps, and strains the molecules of the oils. The gallery providing oil to the bearing surfaces terminates in a relief system that maintains a minimum pressure at high temp and low RPM. The relief system is usually a spring loaded tapered slug with a bypass back to the sump.
We have another element of our lubricants that is often overlooked, and may provide an answer to why racers experience more oil failures with synthetics. It's well known that oils entrain air. This provided a small amount of compressability to the lubricant, and the synthetics seem to be more able to emulsify air than dino oils. I don't know why, but it seems to be so? At high RPM, hgih temp, there may be quite a bit of emulsification of air in the sythetic oil, contributing to the lowered oil pressure. Another factor may be the slop in the pump gears. What is the only engine component that gets unfiltered oil? Yep, the pump gears. Combined, this may have an affect on lower oil pressure with sythetics. Journal failure? Don't know, but Mobil 1 has been qualified for almost every major engine mfg.
The other problem with the low-vis is the base dino that is used. The cracking process separates the crude into a bunch of different bases from light fuel, kerosenes, fuel oils, light lubricants, standard oils, and greases. Taking the molecules out based on viscosity and mass is a true science. One that Doug is much more well versed in than me. For low-vis, there are a package of additives that are added to make up the recipe for a 0-30 or 5-40. Here's another whacked deal - the SAE values for 'viscosity' are not linear with the actual viscosity in cSt. Here's a conversion chart I found online for the actual viscosity range and SAE numbers:
|
| SAE Crank Case Viscosity Number
| ____________________________
| |10| 20 | 30 | 40 | 50 |
| |__|_____|____|_____|______|
|______________________________________________________________
2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 42
viscosity cSt @ 100 degrees C
When a base of SAE 5 is used, it is below 4 cSt @100C, so the additive package needed to make it react like a SAE 30 is pretty signifcant.
So, lots of theory here, but what to put in the crankcase? Very short answer, if you drive on the road, follow the mfg recommendation. Mobil 1 was available in Europe in the summer of 1973, and in the US in fall 1974. So, it could have been specified from new. By the late 80s, sythetics were well established, but if you read the owners manual, it never actually says it's okay to use a synthetic. There is a bunch of blather about 'fuel efficient, or hydrocracked' oils, indicating a synthetic type. I wouldn't hesitate to use a synthetic of appropriate viscosity. I've been using them in my F350 Diesel for years with 260,000 miles.
If racing, well, that's a whole different subject. Hotter, higher shear, more emulsification, side forces, etc. Mobil 1 is found on the track too, but a number of racers have switched back to dino siting better long term lubrication(long term being a relative term in a race engine).
Two things to remember: Never break in an engine on any synthetic. And although it's okay to mix dino and synthetic, it's not reallly a good idea when temps are very cold, due to thermal differences, might cause a breakdown at the journal.
Now, as to pressure. The best pressure for an engine, is one that will provide complete surface coverage of bearings, at all temps, and RPM, with the least pressure. The pressure is only there to force the lubricant into the journal. Any extra pressure wastes energy, increases temps, and strains the molecules of the oils. The gallery providing oil to the bearing surfaces terminates in a relief system that maintains a minimum pressure at high temp and low RPM. The relief system is usually a spring loaded tapered slug with a bypass back to the sump.
We have another element of our lubricants that is often overlooked, and may provide an answer to why racers experience more oil failures with synthetics. It's well known that oils entrain air. This provided a small amount of compressability to the lubricant, and the synthetics seem to be more able to emulsify air than dino oils. I don't know why, but it seems to be so? At high RPM, hgih temp, there may be quite a bit of emulsification of air in the sythetic oil, contributing to the lowered oil pressure. Another factor may be the slop in the pump gears. What is the only engine component that gets unfiltered oil? Yep, the pump gears. Combined, this may have an affect on lower oil pressure with sythetics. Journal failure? Don't know, but Mobil 1 has been qualified for almost every major engine mfg.
The other problem with the low-vis is the base dino that is used. The cracking process separates the crude into a bunch of different bases from light fuel, kerosenes, fuel oils, light lubricants, standard oils, and greases. Taking the molecules out based on viscosity and mass is a true science. One that Doug is much more well versed in than me. For low-vis, there are a package of additives that are added to make up the recipe for a 0-30 or 5-40. Here's another whacked deal - the SAE values for 'viscosity' are not linear with the actual viscosity in cSt. Here's a conversion chart I found online for the actual viscosity range and SAE numbers:
|
| SAE Crank Case Viscosity Number
| ____________________________
| |10| 20 | 30 | 40 | 50 |
| |__|_____|____|_____|______|
|______________________________________________________________
2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 42
viscosity cSt @ 100 degrees C
When a base of SAE 5 is used, it is below 4 cSt @100C, so the additive package needed to make it react like a SAE 30 is pretty signifcant.
So, lots of theory here, but what to put in the crankcase? Very short answer, if you drive on the road, follow the mfg recommendation. Mobil 1 was available in Europe in the summer of 1973, and in the US in fall 1974. So, it could have been specified from new. By the late 80s, sythetics were well established, but if you read the owners manual, it never actually says it's okay to use a synthetic. There is a bunch of blather about 'fuel efficient, or hydrocracked' oils, indicating a synthetic type. I wouldn't hesitate to use a synthetic of appropriate viscosity. I've been using them in my F350 Diesel for years with 260,000 miles.
If racing, well, that's a whole different subject. Hotter, higher shear, more emulsification, side forces, etc. Mobil 1 is found on the track too, but a number of racers have switched back to dino siting better long term lubrication(long term being a relative term in a race engine).
Two things to remember: Never break in an engine on any synthetic. And although it's okay to mix dino and synthetic, it's not reallly a good idea when temps are very cold, due to thermal differences, might cause a breakdown at the journal.
01-26-2005, 10:12 AM
#21
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I have heard it said that the biggest oil issue with a 928 is piston blow by - so whatever oil you put in should be changed frequently? I guess all oils react the same way to this particular maltreatment, or does somebody know better?
01-26-2005, 11:25 AM
#22
928 Collector
Rennlist Member
Rennlist Member
Marton, blowby is a factor, if you track backwards from a failed engine it usually has to do with the usual suspects:
1. Number one reason is too little or too much oil in crankcase
2. Number two reason is aerated oil OR sloshed oil OR evacuated oil
3. Oil type and grade is not the cause. It may be a contributor in a very small way but it is NOT the cause.
Number two is the problematic one, because we don't know ... wait, let me say this again MK .... WE DO NOT KNOW which one, or all of the above, causes catastrophic engine failure. Who are "we"? I, Mike Schmidt, Louie Ott, Mark Anderson, and anyone else I've ever spoken with. Oil is aerated by the crank BY DESIGN or at least as a necessary side-effect of design of a 928. There is always blowby. This increases crankcase pressure which vents to the valve covers in a 32V. NOW:
If at this point the crank has the oil suspended just enough, OR your oil level is low, OR your oil level is high causing greater suspension OR you're banking heavily and possibly starving the pickup and possibly sloshing oil under the cam cover .... oil will get through the positive crankcase ventilation system via the valve cover and into the intake. All of this is foreseen and normal BY DESIGN. BUT if just enough of it happens, for just long enough, then your engine will be either starved for oil or detonate from the oil in the intake or hydrolock from same. A note: I've seen the hydrolock situation twice. From oil. Via intake. In one case the car would not start it was so flooded with oil. However this hydrolock is rarer. Mainstream failures happen IMHO because of pickup starvation and that .....
.... has buggar-all to do with oil type.
1. Number one reason is too little or too much oil in crankcase
2. Number two reason is aerated oil OR sloshed oil OR evacuated oil
3. Oil type and grade is not the cause. It may be a contributor in a very small way but it is NOT the cause.
Number two is the problematic one, because we don't know ... wait, let me say this again MK .... WE DO NOT KNOW which one, or all of the above, causes catastrophic engine failure. Who are "we"? I, Mike Schmidt, Louie Ott, Mark Anderson, and anyone else I've ever spoken with. Oil is aerated by the crank BY DESIGN or at least as a necessary side-effect of design of a 928. There is always blowby. This increases crankcase pressure which vents to the valve covers in a 32V. NOW:
If at this point the crank has the oil suspended just enough, OR your oil level is low, OR your oil level is high causing greater suspension OR you're banking heavily and possibly starving the pickup and possibly sloshing oil under the cam cover .... oil will get through the positive crankcase ventilation system via the valve cover and into the intake. All of this is foreseen and normal BY DESIGN. BUT if just enough of it happens, for just long enough, then your engine will be either starved for oil or detonate from the oil in the intake or hydrolock from same. A note: I've seen the hydrolock situation twice. From oil. Via intake. In one case the car would not start it was so flooded with oil. However this hydrolock is rarer. Mainstream failures happen IMHO because of pickup starvation and that .....
.... has buggar-all to do with oil type.
