Highest CST # You Draw the Line at

[Fallguy]

In a modern engine what is the highest CST # in cold weather you would consider safe to start and engine at say -35c.

Most oils are around 13,000 to 18,000 cst in this temperature range but would you feel safe at double that at 26-32,000 cst?

Would double the cst # cause double the wear at start up from an oil with twice the cst#.

Know lower the cst for start up the better but at what point would you personally back away and choose a cst # to stay under.

 

[Bster13]

Most 5w & 0w oils are in the 7-10k range for reference.

At -35c, I'd be running the absolutely lowest CST I could find. They say most engine wear is at startup under normal conditions...I suppose all the more so at those extremes.

The thing I contemplate is if you going with a lower starting CST, how does that affect your CST at running temps (212F) and possibly too thin an oil?

 

[fsskier]

At 30,000 or above your engine may not start.... probably decreasing engine wear, but greatly increasing starter wear, along with your employers dissatisfaction - when you do not show up for work!!

Simple answer: at these temperatures, why use a 10W30 if a good 5W30 is available?
Why use 5W30, if a good 0W30 is available?

Right now, I am only using 0W30, will switch to my preferred 0W20 as soon as my warranties expire.

Our last two vehicles (tow vehicle and commuter car) motors still seem good at 300,000 miles on 0W20 Mobil 1, so see little reason to run any kind of thick tar in my engines.

 

[ARCOgraphite]

Op: the cold measurement is in units: centi-poise not cSt.
But the way, most cold start wear is due to acid etching of the upper cyl bore - that's caused by high sulphur content fuel and sulfuric acid generation. NOT cold oil.

 

[Bster13]

Not talking down, but more so in curiosity. I've always heard engine wear was due to cold oil not getting to the metal bits b4 they contact each other and wear. Can you cite any articles or test to the acid etching theory? Thx.

Originally Posted By: ARCOgraphite
Op: the cold measurement is in units: centi-poise not cSt.
But the way, most cold start wear is due to acid etching of the upper cyl bore - that's caused by high sulphur content fuel and sulfuric acid generation. NOT cold oil.

 

[justinf89]

Sorry buddy but the lowest it gets here is about 10f. At- 35 id def run syn and id say any would be great.

 

[IndyIan]

So which numbers are we looking at on this chart?
Shell T5 Spec sheet
Cold cranking simulator or MRV?

 

[flatlandtacoma]

Originally Posted By: Fallguy
In a modern engine what is the highest CST # in cold weather you would consider safe to start and engine at say -35c.

Most oils are around 13,000 to 18,000 cst in this temperature range but would you feel safe at double that at 26-32,000 cst?

Would double the cst # cause double the wear at start up from an oil with twice the cst#.

Know lower the cst for start up the better but at what point would you personally back away and choose a cst # to stay under.


I think if you are expecting -35C you would be better off worring about getting a block heater or a garage. And I would be focusing on the thinnest oil I could find, not the thickest.

 

[Bster13]

Viscosity: Kinematic
- cSt at 40°C
- cSt at 100°C

Originally Posted By: IndyIan
So which numbers are we looking at on this chart?
Shell T5 Spec sheet
Cold cranking simulator or MRV?

 

[fsskier]

Block heaters and garages may help sometimes but....

A block heater draws 500+ watts, or 12 KW a day if left on, $1.20 a day, then...

Your work parking lot probably does not have a plug in
Do you put one in all your cars and plug them all in?
When snowskiing in the mountains, free plugins are rare?
Dragging drop cords around every day, setting timers, etc, then some of them spring a leak and disable the vehicle.

A lot of effort and expense, considering that you can just put in the correct oil in the first place at no extra cost!
I think all modern cars will crank and start easily down to -40f using 0W oils, the real arctic (-50, -60) of course would need some help!

Cold wear: Multiple published research papers show increased wear with very thick cold oil.... almost no oil flying off the rods and up onto the cylinder walls until the oil warms and thins. I know of no tests to substantiate Arco's claims on this issue.

My Take: NOBODY recommends 100W motor oil (if there was such a thing) for even continuous running stationary engines.

In cold temperatures most oils effectively are at least that thick, if more is not better, then why would more yet be better yet??

And I want my car to start!!

 

[Ken2]

No doubt about it. If your engine is spec'ed for 5w30, use a 0W-30. If it is spec'ed for 5W-20, use 0W-20. The engine will crank faster, start easier, and have the oil get to the wear points sooner.

If you have a diesel, you need 5W-40.

 

[Fallguy]

German Castrol is likely to be over 30,000 just dont think should run it in cold weather even though it is 0w30.

Yea has a low pour point as a 0w but does not translate into the pumpability numbers as they are higher than many 5w oils on the low temp mrv numbers.

 

[addyguy]

GC is a 0W oil, so it has to be under 6200cp @-35C to qualify.

It DOES NOT have higher pumbability numbers than a 5W - they are tested at different values!!!

You are not comparing apples to apples here - you need to learn the values different things are tested at in the API sequence chart!

 

[fsskier]

Well said Addyguy!!!

Another one we hear a lot is "XwX is thinner in cold than XWX", then quote the numbers for 40C as the cold numbers.

Now, 40C is the same as 104F, perhaps, that is a cold start in the Sahara, but not in the wintertime plains states!!

 

[Bster13]

If an oil is thinner than another oil at 40c, then it'll be a ~heck~ of a lot thinner (better) than that same oil at 0c (32F).

 

[fsskier]

Is this not a contradiction to the pdf that you submitted in an earlier post???

Now the numbers for 32f are not given, but:

The 5W30 is thinner than the 0W40 at 40 C
The 0W40 is thinner at -35 than 5W30 is at -30!!

That means the 0W40 is much thinner, in a temperature range where viscosity is rising dramatically.

Re read the charts carefully. Note that viscosity is rising rapidly, if one oil has the same viscosity at -35c that another has at -30c, it is MUCH thinner in cold.

 

[Bster13]

I did not submit a PDF in this thread. Someone did asking what values from the PDF they should be concerned about.


But you are correct... I assumed based off the default "0c" setting of the chart.

So up until about -16c (5F), the 5w30 is better for cold starting then the 0w-40 starts to look better.

That does not make logical sense to me because I thought the "-40" held back the "0w" when it got cold. Can anyone lay it out in layman's terms?

 

[CATERHAM]

The OP is really asking the wrong question as even the lightest PCMO you can buy (M1 0W-20, MRV @-40 10,400cP) is too thick for optimal starting and running at super cold temps like -35C, but it minimizes the associated problems.
Furthermore even for vehicles that specify a 30wt oil it's still better to use a M1 0W-20 since normal operating oil temps WILL NOT be acheived under any circumstances at those temps.
If you still feel you must run a 0W-30, the lightest available is Petro-Canada's 0w30 (if you can get it) with it's MRV of 14,204cP. It puts M1 0w30 to shame at 17,100cP.

 

[21Rouge]

Originally Posted By: CATERHAM
If you still feel you must run a 0W-30, the lightest available is Petro-Canada's 0w30 (if you can get it) with it's MRV of 14,204cP. It puts M1 0w30 to shame at 17,100cP.



It isn't even close to a fair fight in this respect is it?
But then again I don't have a true feel for the real world difference for every say...1000 cP increase or decrease in this pumping viscosity. Maybe it isn't as dramatic as the numbers seem to indicate.

 

[CATERHAM]

It is as dramatic as the numbers indicate, but then very few of us ("in the real world") have experienced temps down to -40 degrees.
The MRV viscosity measure is not called "borderline pumping" for nothing. At that temperature the viscosity curve is so steep that a further drop in temperature of just one degree Celsius can increase the oil's viscosity by 30%.

At something just a bit warmer than -40, say around 38C, I'm sure M1 0W-30's MRV would be the same as PC at -40. In that sense they are fairly close.