Cold Start Thickness - Dr. Haas

[BuickGN]

Originally Posted By: AEHaas
Originally Posted By: oilyriser
Is cavitation during start up an issue? High viscosity should prevent oil from re-entering the suction region downstream of the load carrying part of the oil film, in a bearing.


Many high revving sports cars sustain engine damage by the user turning the engine on then fully revving it for sound effects. I believe this is a result of cavitation at multiple sites.

aehaas


If it's dead cold but then this practice would be considered abuse. Cavitation can also happen with a fully warm engine if revved too high. I've watched my friend's Porsche lose oil pressure when revved 1,200rpm past the stock limiter fully hot on a 100 degree day.

There's cavitation when the engine is revved too high and the oil is cold and thick but oil pressure can also fall off at very high rpms because the pump can't keep up with the flow requirements.

 

[Gary Allan]

Originally Posted By: AEHaas
Here is one reference:
Development of the Sequence IV A Valve Train Wear Lubrication Testart 1, Sagawa et al:
Viscosity data reveals that the more viscous oil did not significantly alter the cam angle of minimum oil film thickness. Of greater importance is the finding that the higher viscosity oil continued to exhibit boundary layer lubrication. (Ergo thicker is not necessarily better).
The effect of engine intake air humidity was significant so that tests are now done with specified humidity conditions.
It was postulated that fuel dilution of oil would elevate cam wear. Fuel dilution of 4.5 percent did not effect wear. (This would have the effect of lowering the viscosity about 1 grade).


Thanks for the humidity reference. I don't know if we can transfer the cam wear observations (or lack of them) to cylinder/ring wear..but it does nudge in the right direction..

 

[Gary Allan]

Originally Posted By: BuickGN


I'm assuming those numbers are for dino oils?

My straight 30 synthetic has a 66.3cst at 75, better than the 10w-30. Those look like worst case scenarios.


Then your straight 30 also qualifies as 000W. ACD is a SAE 30 that has a 40C visc of 66.3. @ 75F/24C it should be around 140 Cst. I don't think that we have lubricants with that broad a VI to achieve that low a visc at that low a temp. I think it would have a VI of 240+ (check my math).

 

[BuickGN]

Originally Posted By: Gary Allan
Originally Posted By: BuickGN


I'm assuming those numbers are for dino oils?

My straight 30 synthetic has a 66.3cst at 75, better than the 10w-30. Those look like worst case scenarios.


Then your straight 30 also qualifies as 000W. ACD is a SAE 30 that has a 40C visc of 66.3. @ 75F/24C it should be around 140 Cst. I don't think that we have lubricants with that broad a VI to achieve that low a visc at that low a temp. I think it would have a VI of 240+ (check my math).


Oops. You're right. I was looking at the 75 number and thinking of 40c in my head. Still though, it's half the viscosity of the straight 30 in the example.

 

[Gary Allan]

Well, now that you mention it (looking at the other figures), I don't think any of them were presented for the "truth" of what they say ..but more for demonstration purposes.



0w-30 would be 113 Cst @ 75f/24C with a VI of 173 and a 40C visc of 56.6Cst.

 

[Taylor]

Dr. Haas,

While I agree with you, I think the "flow" numbers are a bit misleading.

 

[expat]

Is there any data from people who have fitted air to oil, oil coolers. where the oil can be cooled excessively, regardless of the engine temperature?
I'm thinking here of the the British MGB, that was fitted, in north America, but not in the U.K., with an oil cooler. The owners seem to favour 20w-50m oil (regardless where they live) but it seems, the engines appear to have about the same life expectancy!

 

[XS650]

Originally Posted By: Gary Allan
ACD is a SAE 30 that has a 40C visc of 66.3. @ 75F/24C it should be around 140 Cst.


ACD is only a "straight 30" because it wasn't submitted for xW testing. Another case of "use where recommended" because if it were actually qualified as what it is, the straight 30 fanatics wouldn't buy it.

 

[Doug Hillary]

Hi,
ADFD1 - You quote this from the papers:
"I have heard several people say that Porsche specifically prohibits a 0W-XX engine oil, that it is too thin."

This is totally untrue! Porsche have recommended 0W-40 (and 5W-40) lubricants for all >MY84 engines since around 1999. In fact I have just returned from Germany and I can confirm that Porsche prefer 0W-40 lubricants and even in their new DI engine families still go for two years or 30k kms OCIs

After speaking with many Privateer Porsche racers at the Nurburgring, and many Owners it is clear they also use 0W-40 viscosity lubricants

Older aircooled race engines get anything from 5W-40, through 15W-50 to 10W-60 viscosities. The Museum uses 20W-50 or 15W-40 mineral lubricants in their old "classic" race car engines (incl flat 12s). These are raised to 80C before load or revs are applied

Porsche steadily moved from the 15W-?? lubricants specified in the 1970-1980s to 5W-40 and 0W-40 lubricants. This commenced with 5W-40 in the mid 1980s. This viscosity became their factory fill for most engines in MY92. This is in order to get the valve train components working promptly and for startup wear minimisation

Mercedes Benz use a 5W-30 viscosity synthetic as the initial startup/test lubricant at their Unterturkheim engine plant

In most engines it is desirable to use the lowest viscosity lubricant specified by the engine's manufacturer for the application and ambient temperature range expected

 

[ADFD1]

Originally Posted By: Doug Hillary
Hi,
ADFD1 - You quote this from the papers:
"I have heard several people say that Porsche specifically prohibits a 0W-XX engine oil, that it is too thin."

This is totally untrue! Porsche have recommended 0W-40 (and 5W-40) lubricants for all >MY84 engines since around 1999. In fact I have just returned from Germany and I can confirm that Porsche prefer 0W-40 lubricants and even in their new DI engine families still go for two years or 30k kms OCIs

After speaking with many Privateer Porsche racers at the Nurburgring, and many Owners it is clear they also use 0W-40 viscosity lubricants

Older aircooled race engines get anything from 5W-40, through 15W-50 to 10W-60 viscosities. The Museum uses 20W-50 or 15W-40 mineral lubricants in their old "classic" race car engines (incl flat 12s). These are raised to 80C before load or revs are applied

Porsche steadily moved from the 15W-?? lubricants specified in the 1970-1980s to 5W-40 and 0W-40 lubricants. This commenced with 5W-40 in the mid 1980s. This viscosity became their factory fill for most engines in MY92. This is in order to get the valve train components working promptly and for startup wear minimisation

Mercedes Benz use a 5W-30 viscosity synthetic as the initial startup/test lubricant at their Unterturkheim engine plant

In most engines it is desirable to use the lowest viscosity lubricant specified by the engine's manufacturer for the application and ambient temperature range expected


Thanks Doug!

I was quoting what I read and searching for answers to satisfy myself. My thoughts are use what the mfg specs, and I favor anything 0W because of better flow at start up in most cases, especially during extreme cold.

A 0w-xx might be slightly better in some cases depending on how cold it is. The 0W-xx oils do have some added protection benefits during the time it takes for the oil to reach operating temps? Is this logic correct?

I'll toss in this monkey wrench. There could be a 5W-xx oil with a lower temp pour point than a 0W-xx in that event it would offer better start up protection, as long as the mfg specs that grade for that application and ambient temp range expected?

Many Thanks!
AD

 

[AEHaas]

Originally Posted By: expat
Is there any data from people who have fitted air to oil, oil coolers. where the oil can be cooled excessively, regardless of the engine temperature?
I'm thinking here of the the British MGB, that was fitted, in north America, but not in the U.K., with an oil cooler. The owners seem to favour 20w-50m oil (regardless where they live) but it seems, the engines appear to have about the same life expectancy!


From an earlier post of mine:

Most interesting to me was the way they tested wear at lower, start up, oil temperatures. In a previous study (1) they start with room temperature engines and oil showing the trend of decreasing wear as the engine heated up. In the current study they actually took a hot engine and chilled the coolant and oil from that of the normal operating temperature to a coolant temperature of around 80 F and oil temperature to 70 F. As the temperatures fell the wear increased. It reached the same rate of wear as the 4,000 RPM full load WOT. This was with the load at the minimum level. The fluids were then allowed to heat back up to normal operating temperatures and the wear rates normalized (decreased).

Wear at room temperature oil was 20 times higher than wear at normal operating temperatures. This finding is what closed the article. They stated that this will be the next focus of their upcoming research.

aehaas

(1) Effect of Break-In and Operating Conditions on Piston Ring and Cylinder Bore Wear in SI (Spark-Ignition) Engines, Schneider et al:
The rate of wear is much higher within 15-20 minutes of start-up than after reaching normal operating temperature. There was a lot of data but I conclude that the initial start-up time period (first 20 minutes) result is 100 nanometers of wear whereas the steady state wear rate was only 4 nanometers per hour thereafter. (Hence we should be concerned about start-up oil thickness more than running thickness. This justifies the statement that 95 percent of engine wear occurs just after start-up.)

 

[AEHaas]

Incidentally, I just conversed with Eric W. Schneider and found out they nixed his research at GM on low viscosity motor oils and start up wear. "...there are other pressing priorities at the moment."

'Bad news for us trying to figure this one out.

aehaas

 

[Jim Allen]

I just want to say that this discussion is in the best traditions of BITOG and it's like was the primary reason I joined this group. While these intense-but-civil "meat and taters" discussions are somewhat fewer than in the past, they are well worth waiting for! Kudos to all contributors!

With regards to startup wear:

On a cold start,most engines go to a fast idle. Many EFI engines "flare" up to 1500 or so on a cold start, then gradually come down to an idle speed. How does this enter into the cold flow equation? There isn't much load on the engine but it seems intuitive that the engine could use a few more seconds of low rpm to stabilize flow and pressure. Of course, EFI engine have to crank a little before start and maybe that's enough (they don't instantly "lite" like some older engines).

 

[demarpaint]

Great point Jim! I'm enjoying this thread too.

It's a shame they can't program into the EFI start-up a second or two of lower rpms just to get some oil around before the engine goes up to 1500 rpms. My new Jeep seems to come to life a lot faster when starting than my older Fords do, the seem to crank a tiny bit longer.

 

[Taylor]

Jim,

That is indeed an excellent point, as I'm sure you know the engine start-up speed is highly dependent upon the vehicle. I also believe that the ambient temp plays a role as well. For example in the summer my jeep seems to start up to around 1200 rpm's and drop to 1000 rather quickly, however in the winter it likes to stay at 1200 rpm's a but longer. It sometimes, initially, spikes a bit higher. I usually wait untill it drops to at least 1000 rpm's before I shift into drive, once a load is placed on the engine it drops to idle.

 

[demarpaint]

Ambient temps play a big role in the fast idle speed as well as how quickly the engine drops to normal idle speed.

I've seen engines used in some really pour driving conditions go well over 100,000 miles. Even when driven 4 or 5 times a day 1- 2 miles then shut off for a few hours, and done over and over again.

 

[Taylor]

Me too, my 4.0 has about 175,000 mi of it My crank bearings are also showing copper, but that may be b/c my brother owned it before I and he used a 1/2 40w 1/2 Lucas blend. AHHH!

 

[Gary Allan]

Originally Posted By: XS650
Originally Posted By: Gary Allan
ACD is a SAE 30 that has a 40C visc of 66.3. @ 75F/24C it should be around 140 Cst.


ACD is only a "straight 30" because it wasn't submitted for xW testing. Another case of "use where recommended" because if it were actually qualified as what it is, the straight 30 fanatics wouldn't buy it.


It qualifies as both SAE 30 and 10w-30. It's the only Amsoil product with absolutely no VII.

It's a dessert topping!
It's a floor cleaner!

It's both!

 

[Gary Allan]

Quote:
Hi,
ADFD1 - You quote this from the papers:
"I have heard several people say that Porsche specifically prohibits a 0W-XX engine oil, that it is too thin."

This is totally untrue! Porsche have recommended 0W-40 (and 5W-40) lubricants for all >MY84 engines since around 1999. In fact I have just returned from Germany and I can confirm that Porsche prefer 0W-40 lubricants and even in their new DI engine families still go for two years or 30k kms OCIs



That's just the entrails of people not knowing what the cold spec's mean, Doug. We still run into it here.

Now if those same people said that 0w-X oils may sheared like sheep at the Forbes grafted in heraldry Scottish trials of passage round-up on their summer retreat islands ...that might be another story ..as much as it may or may not be an issue of merit...

 

[ADFD1]

Originally Posted By: Gary Allan
Quote:
Hi,
ADFD1 - You quote this from the papers:
"I have heard several people say that Porsche specifically prohibits a 0W-XX engine oil, that it is too thin."

This is totally untrue! Porsche have recommended 0W-40 (and 5W-40) lubricants for all >MY84 engines since around 1999. In fact I have just returned from Germany and I can confirm that Porsche prefer 0W-40 lubricants and even in their new DI engine families still go for two years or 30k kms OCIs



That's just the entrails of people not knowing what the cold spec's mean, Doug. We still run into it here.

Now if those same people said that 0w-X oils may sheared like sheep at the Forbes grafted in heraldry Scottish trials of passage round-up on their summer retreat islands ...that might be another story ..as much as it may or may not be an issue of merit...


Gary I always look forward to your replies as well as Doug H.

I'm trying to figure out where I quoted anything from Porsche? Was I asleep? Did I miss something? I think Doug has me mixed up with someone else

Although I'm gathering some good info from this thread.

I was quoting from Dr. Haas IIRC I mentioned that above.

AD