Synthetic oil properties approaching pour point.

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We have experienced an engine failure (cited by the manufacturer as having run with no oil in the engine) during a cold chamber test at -40c (-40f). The oil used was Eni 5w-30 iSint fully synthetic. The pour point spec is -42c (-43.6f) The engine damage is consistent with having suffered oil starvation, in that the crank bearings have overheated and failed. Ultimately there was a catastrophic failure of one of the con rods, which made a break for freedom via the crank case.The rods are blued for 3/4 of their length which would indicated that they have not been cooled at all during this process.

The system has a low oil pressure shutdown facility and high oil pressure was seen during the 2 minutes that the engine ran prior to failure. We are reasonably certain that although oil pressure was present, there was no oil flow through the filter. We think this because although there are lots of particles in the sump, including a very fine metallic powder, there are no particles in the fine gauze of the oil pick up and the oil filter medium is completely clean (was replaced just prior to the test).There is also no fine grey dust present in the tube of the pickup.

We need to be sure that the reason for the failure is that the wrong spec oil was used, in that the pour point was within 2 degrees c of the test temperature. I have trawled the internet to find out what happens to a synthetic oil as it approaches its pour point (can't find a thing) in an attempt to understand the physical properties of the oil used and if those properties would lead to a lack of oil being pumped around the engine.

If anyone can point me in the right direction? Thanks.
 
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Welcome to BITOG!

Interesting question that hopefully someone will shed some light on for you.

I was just curious, why do you do these cold chamber tests? And what equipment/engines do you test? Is it some industrial gear that needs to run in arctic circle?

Have you carried out a similar test successfully with other oils? Which ones?
 
Maybe Eni lies about specifications? Aren't they government owned? Could be whatever oil was cheapest on tap at the local refinery?

Just because an oil will pour at a certain temperature doesn't necessarily mean it will lubricate and protect at that temperature. Probably should have warmed the engine with a block heater or at least idled it for 20-30 minutes before commencing testing.
 
Originally Posted By: Cardenio327
Just because an oil will pour at a certain temperature doesn't necessarily mean it will lubricate and protect at that temperature.

Exactly. The pour point spec is not all that useful. That's why we have specs such as MRV and CCV.

If you're faced with temps as low as -40C, I believe a 0w-XX oil would probably work best.
 
Another thing, even though the oil supposedly has a pour point of -42 °C, it is a 5w oil which means it only has to be approved to perform at -35 °C. 0w oils are approved to perform at -40 °C.
 
What engine? It doesn't sound like a lubrication issue to me, especially if you have oil pressure and the con rods were blue from heat in -40 temps. What RPM was the engine running at? I wonder if there was a bypass valve issue due to the cold
 
Right a 5W-30 oil will not pump at -40.
Any 0W-XX oil will pump at -40 degrees although oil flow will still be marginal until some heat gets into the oil to start thinning it out.
PP is a very misleading spec' which is best ignored. As QP pointed out that's why the borderline pumping MRV spec' was developed.
 
Originally Posted By: Zaedock
It doesn't sound like a lubrication issue to me, especially if you have oil pressure and the con rods were blue from heat in -40 temps. What RPM was the engine running at? I wonder if there was a bypass valve issue due to the cold

Of course you can have maximum OP but the by-pass valve will be fully open. That said, catastrophic engine failure would not likely have occurred if the engine rev's were kept as low as possible (1,000 rpm) until the oil started to thin out and the oil pump came out of by-pass mode. I suspect the engine was running at some elevated rev's.
 
Originally Posted By: CATERHAM
I suspect the engine was running at some elevated rev's.

Yeah, it would be nice to know the details of this "cold chamber test."
 
It sounds as though you tried to run past the limits of what a 5W-XX oil is supposed to do. The symptoms of oil starvation you describe are exactly those that prompted the development of the Cold Pumpability spec by the SAE in the 1970's. Some oils turn into Jello if they are brought down to deep freezing temperatures slowly, and cannot be pulled into the oil pump when the engine starts. The oil pump pickup will suck a hole in the semi-solidified oil, then the engine will starve for oil

A 5W oil is qualified for its Cold Pumpability spec at -35C, so if you were trying to use it at -40C, you were asking too much of it. We know from looking at low temperature oil specs that another 5C of cooling in the -30C range can double the viscosity. Depending on the Pour Point rating in this case sounds like a mistake.
 
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The pour point test only measures the temperature, in 3°C increments, that the oil last "poured" under its own weight. Pouring is defined as any movement in the oil surface during a five second period of holding the test jar horizontally, hence the oil is not really "pouring" and in fact is barely moving. The test reproducibility is +- 3°C, so if one lab gets a -42°C test result, another lab could get -36°C.

In any case, as others have said, the pour point test is not a good indicator of oil pumpability, for which the industry uses the Cold-Cranking Simulator (CCS) and the Mini-Rotary Viscometer (MRV) tests. By these tests a 5W-X oil is generally not suitable for starting an engine at -40°C.

Tom NJ
 
I have to agree 100% with the above posters. I think you are confusing pour point with pumpability. The two are not the same. Take a trip over to YouTube and check out the pour point videos for various oils. You'll laugh at the thought that an oil in that condition can lubricate anything. The pour point test, as defined by ASTM D97, only needs to show that the oil has some movement on its surface over the course of some period of time(I forget how long. A few seconds I think) time at X temperature and 90 deg tilt angle.

Edit: it seems everything I just said was already said by Tom NJ, and said better. Fantastic job at explaining that, Tom.
 
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Originally Posted By: CATERHAM
Right a 5W-30 oil will not pump at -40.

5w-30 will pump at -40, even conventional, just not particularly well. I've never had an engine experience something like this, and do you know how many Saskatchewan winters I endured before I got a garage, much less my heated one?

But, as you mention, pour point isn't terribly useful in this case. And I'd also be fairly confident that this engine wasn't at idle when this happened.

If an engine blows up from one -40 test, either the test is extremely demanding (i.e. like you said, revs not below 1000), or the engine had some issues already. A 5w-30 (that actually meets the specifications) is certainly not the culprit here.
 
Oil near the pour point looks like snot. Big "globs" of semi-solid fluid surrounded by a layer of "goo" that's semi-fluid.


You gotta remember that the pour point is the point at which there is NO movement at all.

Typically, in the refrigeration systems I deal with, you can not operate lower than 10º above the pour point. This point is typically called the floc point (only for hydrocarbon based fluids though). This is when the waxes in the oil begin to solidify and get nasty.

So basically, your oil pump was trying to pump "snot". It would be unable to force it through the small capillaries effectively.

I'm kind of curious how your oil temp could be reaching anything close to the pour or floc point of the oil given you were operating in only -40º ambient temperature. Engines release almost 25+% of the fuel energy as pure heat.... so how did the oil get THAT cold? Dry sump system?

This is why refrigeration systems have oil heaters.
 
Originally Posted By: camel
I'm kind of curious how your oil temp could be reaching anything close to the pour or floc point of the oil given you were operating in only -40º ambient temperature. Engines release almost 25+% of the fuel energy as pure heat.... so how did the oil get THAT cold? Dry sump system?


I would expect they froze the motor overnight in the chamber at -40 °C then fired it up with little or no idling time and started testing it under load on a dynometer. Perfect conditions to starve the bearings of oil.

Anyone that actually uses a car in those temperatures drives slow and easy, especially when starting out. Anyone using mining or trucking equipment is going to let the engine warm up at least half an hour so that the inside of the cab halfway defrosts before they start working.
 
Absolutely. Up here, if it's -40 out, it's just about impossible to hop in, start it, and "drive away gently" as is the normal recommendation. You sit there for a few minutes or, as you indicate, you're not going to be seeing anything. And then, you drive it sensibly until it's adequately warm.
 
I fully agree with all of what's said above! No need to repeat it.

However, I'd also like to add that some oils perform quite a bit better during cold operations. In the aviation world, we regularly require a turbine engine oil to pump at very cold temperatures. It's not unusual for an aircraft to depart my home base of West Palm Beach, Florida and land in Anchorage, Alaska as it's first overnight stop.

When I worked for Mobil Oil, the engineers did some cold weather testing that ensured reliable oil pumping at -40. The difference between oils was staggering.
 
Wow! just got back to work this morning and i wasn't expecting much in the way of responses. Wrong! It will take me a while to go through all the points raised and i will try to compile one complete answer to all the points raised later today. Taz.
 
From everyones comments, it seems that as we thought, the oil pressure was present but no oil flow, due to the temp. Unit is enclosed and preheated for 30minutes via a diesel 5kw pumped water jacket heater, which also heats the fuel lines. The wet oil sump is not heated as there is insufficient available power resources to do this. Engine indicated water temp is 79c at 15minutes and a further 15min heat soak prior to start up. Thermostat open temp is 82c. The spec requires the unit to start and run at 3000rpm immediately.

'On load' from engine driven 30kva alternator is provided at 30seconds. manual states that for anything below -15c, 0w-30 oil should be used. The customer has used 5w-30 by mistake.

It is clear that oil pressure was available, (the sensor for low oil pressure shutdown operates correctly post failure) but oil flow did not reach the oil filter as there was zero debris in the filter medium or in the sump filter gauze, indicating that no oil was picked up from the sump.

Oil that we use for testing in the cold chamber is Mobil 1 0-30w. Unfortunately the customer did not have this available.

Thanks for all the advice.

Does an oil rated at 0-xxW have to meet a specific minimum pour point? The only reason I ask is that the customer wishes to include this pour point value in the manuals, so that it is clear. However, I would have though that there are criteria that an oil has to meet in order to qualify as a 0-xxW rated oil?

Clearly they have selected the wrong oil for their test and are attempting to mitigate future occurrences.
 
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