Synthetic cold weather performance?

Pennzoil motor oil
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meborder

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it is often said on here that synthetics outperform conventionals when it comes to cold weather performance.

so my question is will a 5w30 synthetic with a Viscosity @ -30ºC of 5,544 cP
outperform a 5w30 conventional with a Viscosity @ -30ºC of 5,380 cP?

what constitutes "cold weather performance"?
something more than the viscosity at a given temperature?

FWIW, these are actual numbers of two oils i am currently using. so i'm wondering which is actually better for winter use.
 
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My guess is that the synthetic will retain it's cold
weather performance longer as the oil ages
than the conventional 5W30.

Also, the oil with the higher VI will likely have better cold-
flow and cranking performance below -30C.

Funny thing, the same people who tell us not to put any
weight on the pour-point spec, will make videos of chilled
engine oil dumping out of test tubes.

Go figure!
 
Originally Posted By: meborder
...so I'm wondering which is actually better for winter use.

A day after our northern hemisphere's summer solstice. You're a man who likes to plan ahead!
 
fair enough

the synthetic 5w30 has a pour point of -42°C
the conventional 5w30 has a pour point of -38°C

so, it is slightly lower, but is there more to it than that?
 
Originally Posted By: splinter
Originally Posted By: meborder
...so I'm wondering which is actually better for winter use.

A day after our northern hemisphere's summer solstice. You're a man who likes to plan ahead!


one likes to buy his oil when it's on sale
smile.gif
 
Originally Posted By: meborder
Viscosity Index for synthetic is 161 and conventional is 160


Don't worry about VI, it means squat below 0C.
 
Define synthetic? What synthetic base oil or blend are we referring to synthetic?
 
Originally Posted By: OVERKILL
Originally Posted By: meborder
Viscosity Index for synthetic is 161 and conventional is 160


Don't worry about VI, it means squat below 0C.
Especially on a finished lube. The VI on the base stock before blending tells more.
 
Synthetic should allow you a longer OCI, that's about it. All the cold temp. performance is largely blown out of proportion. Even if synthetic is slightly thinner at those extreme temps, it will not protect the engine any better as long as the outside temp. isn't lower than the "W" rating of the oil.

The only other advantage of a synthetic oil, that could be worth mentioning, is that at those extremely low temperatures, the synthetic will have less wax chains forming, but we're talking largely group IV and up. Hydrocracked group III is probably about the same.
 
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Originally Posted By: Garak
Check the MRV for a better measure than CCS, and far better than VI or pour point.


where can one find this spec for various oils?
 
Krisz,
that's what I was about to say...the high end GrIII, and the IVs should have little to no wax, and will therefore be more predictable (I've got a virgin 10W30 syn blend in my freezer that stops flowing after a fortnight at -19C, about the same as a dino SAE30 after a couple of days).

Time and (lack of) temperature let it set up. The standards are specific cooling rates and temperatures, based on some semblence of usage, not a month at -19C solid.

So synthetic should be more predictable there.

Oils within a "W" category are allowed to slip a category during use, so a 5W can become a 10W during use and still be labelled a 5W.

So if planning a long OCI, a Synthetic should see out a longer OCI with less risk...still be worth getting a "W grade" lower than your lowest ambient temperature 'though.
 
Originally Posted By: Shannow

So synthetic should be more predictable there.

Oils within a "W" category are allowed to slip a category during use, so a 5W can become a 10W during use and still be labelled a 5W.

So if planning a long OCI, a Synthetic should see out a longer OCI with less risk...still be worth getting a "W grade" lower than your lowest ambient temperature 'though.


Fully agree there. Also, another route, which is what I do, instead of getting a lower 'W" rated oil is simply to put in fresh oil just before the winter.

I believe the oil aging and retention of the cold properties is part of the new oil standard, at least in Europe, because few years ago European manufacturers experienced an increased number of engine failures during winter. It was attributed to the oil losing its cold pumpability properties due to very long OCIs they have there and of course an abnormally cold winter.
 
Originally Posted By: meborder
where can one find this spec for various oils?

Check the data sheets. Unfortunately, some publish these numbers, and others do not, and sometimes there is no clear policy within a company across different lines of oil, even.
 
Originally Posted By: meborder
wasn't hydrocracking invented to get rid of the wax chains?

maybe i got it wrong, but that was always my understanding.


Don't think so. Was a chart posted a while back that showed the difference between Group III and PAO at -30C and it was staggering. Member bobbydevro stated that this was why they used PPD's, to deal with the wax issue, a problem PAO doesn't have.
 
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