Cold weather synthetic engine oil question: how low?

[Paul Lutes]

Full synthetic 0W-40: any body used it below -20 F without an engine block heater? If so, what oil brand and what vehicle?

If I'm asking a silly question, it's because I'm from California and have no car-fu.

 

[scott43]

One time shot? 0W40 is pretty thin to begin with. I routinely drive my cars with 5W30 in -20F when we get cold spells. Two years ago it didn't get over freezing for 3 months here. Every night was -20F for two month. Cranks slow sometimes..but overall not worried. If you're contemplating moving to North Dakota for the winter or longer you may want to consider a block heater next time around.

 

[Dakine]

The 0 is a measure of the viscosity of the oil when it is cold.
The 40 is a measure of the viscosity of the oil when it is hot.
The only time I use 0wsomething oil is when it is very cold.
The best advice is to use what your owner's manual sez.
What this oil really will do is cost you a skinch (American, not Metric Skinch) of gas mileage when it is warm and you are cruising.
During summer I prefer to run a 5w oil in a newish car and a 10w oil in a higher mileage unit because it gives the bearings a bit more protection during cold starts.
But my old outlaw Harley prefers straight 60 weight Kendall GT-1 dino oil like do most roller bearing engines.

 

[oldschoolskier]

I agree with @scott43 synthetic is thin to start with, so if you have an oil sweat you will have a leak. That said consider the numbers vs the type to start. 0w40 means 0 how it performs at cold temps (ie how thick it gets when cold), 40 is how thin it gets hot. The difference here with a synthetic is is starts thin and doesn't get thinner hot or thicken cold as much as regular oil does.

As to your question which Brand, well some are definitely better than others.

From personal experience, document your mileage over several tanks with a standard oil, switch to a synthetic and compare, switch brands and compare. The right oil improves gas mileage the wrong reduces it. How much, potentially as much as +/- 20%. My simple view on this is better mileage means less friction therefore less wearand longer engine life.

While synthetic oil is more expensive it generally lasts longer so bigger intervals are possible which results in about similar costs (in most cases).

How do I judge when the interval is correct, when I see a drop in mileage (oil has stopped performing). A lot of modern engines are designed to work with synthetics so it’s a bit of trial and error to find which is best for you.

Edit (add) the thinnest oil you can use while providing protection you need is the best oil.

My ‘11VW uses 5w40 and my 14F150 uses 0w20 both are rated up to15k km for oil changes, change very 10k km regardless (simple math and matches finger count ). Go figure.

 

[Dakine]

"I agree with @scott43 synthetic is thin to start with, so if you have an oil sweat you will have a leak."
That is incorrect.
A 10w30 or whatever oil is the same viscosity regardless of whether it is based on synthetic or dino stock.
These numbers are derived from viscosity testing and the type of oil is not a factor.
That said, some synthetic oils do tend to weep through gaskets because they have different wetting characteristics and do not swell the gaskets as much as dino oils.
Most synthetics now have additives that make this a non issue.
All oils get most of their viscosity properties from additives and not the base stock.

I cannot possibly see how oil type can make a 20% difference in gas mileage.
If there is enough friction in an engine that it uses 20% more fuel something is seriously wrong and you will soon have pieces.
Maybe oldschool meant 2% which is a credible figure but also very hard to measure accurately.
Modern engines which have very tight bearing clearance specs require thinner oil.
Stick with your car's recommended oil viscosity and change intervals, factory engineers really do know what they are doing!
The type of oil filter you use affects engine longevity far more than the type of oil you choose.
This is a whole other subject full of myth and marketing......

 

[Tom K.]

Our Sienna with no block heater uses 0-20 full syn, and I'm always astounded how easily it cranks over at my in-laws in Butte MT at Christmas.

Two trips over the years have hit minus 40.

But I can't recall whether that was F or C.

 

[scott43]

There are cold weather oil viscosity specs sometimes if you check your manual. But that's generally if you're spending the entire winter in cold conditions.

 

[sparty]

There are cold weather oil viscosity specs sometimes if you check your manual. But that's generally if you're spending the entire winter in cold conditions.

...but you also want to look at the fine print to see what is considered "cold" conditions. On a previous vehicle (I can't recall which one), I found that the OEM spec for "severe winter weather" matched northern New England. I mean, yeah, we get winter but it's not like North Dakota or the Canadian plains...

 

[Paul Lutes]

Excellent input - many thanks! Pretty sure the MFG recommended oil is Mobil FS 0W-40 - will verify later today. It's for a MB GLC 43 coup AMG. Looks like all their AMGs get 0W-40. It sounds like I should be fine - especially if I can hook up with some enclosed/underground parking!

 

[Snowfan]

Bob is the oil guy. Ask him (them).

https://www.bobistheoilguy.com/

https://www.bobistheoilguy.com/forums/ubbthreads.php/forum_summary

 

[Tom K.]

Excellent input - many thanks! Pretty sure the MFG recommended oil is Mobil FS 0W-40 - will verify later today. It's for a MB GLC 43 coup AMG. Looks like all their AMGs get 0W-40. It sounds like I should be fine - especially if I can hook up with some enclosed/underground parking!

What?! Why stop at 43, when the numbers go up to 63?!

 

[scott43]

Looking at the Mobil tool, 0W30 is also rated for that vehicle. So you could use that and it'll be slightly less viscous when cold. Having said that, if you're only making occasional trips to the frozen wilderness I wouldn't bother.

 

[Paul Lutes]

What?! Why stop at 43, when the numbers go up to 63?!

Cuz I'm light and agile, not heavy and brutish?!?!

 

[Dakine]

Looking at the Mobil tool, 0W30 is also rated for that vehicle. So you could use that and it'll be slightly less viscous when cold. Having said that, if you're only making occasional trips to the frozen wilderness I wouldn't bother.

No it won't be less viscous when cold.
It is a 0 weight oil when cold and a 30 weight oil when hot.
Modern oils have a very non-linear viscosity-temperature curve.

 

[JohnnyG]

I (and many others in a car club) used Castrol 0w30 Syntec in our Subaru's year round. Although, it was quite specific that you could find the German Castrol, meaning it is the only one still made in Germany you could find.

Just browse Google for German Castrol or GC and you'll find everything you need. It's a very good oil, and highly recommended.

 

[Dakine]

Of course you could run Shell F1 which is used in F1 cars.
500$ a quart.
Most synthetic oil is about extending change intervals and increasing gas mileage.
The type of oil you run will not affect the longevity of your engine as long as you use the appropriate change intervals.
The cheapest dino oil will be fine as long as you change it every 2000 miles.
This is not true for gearboxes and hot running air cooled engines where synthetics really make a difference.
Like I said before, the type of filter is a key part of your oiling system.

 

[scott43]

No it won't be less viscous when cold.
It is a 0 weight oil when cold and a 30 weight oil when hot.
Modern oils have a very non-linear viscosity-temperature curve.

Yes you are correct. My mistake.

 

[scott43]

This is not true for gearboxes and hot running air cooled engines where synthetics really make a difference.
Like I said before, the type of filter is a key part of your oiling system.

I have seen bulletins for some motors that have changed to synthetic-only because of sludge build-up in the head, liquid cooled engines. But synthetic is so common now as an OEM spec that those days are probably over.

 

[sparty]

Synthetic often has a higher cook point, as well (i.e. can reach a higher temp while still performing within specifications), where dino oil, once past a certain temperature, will never again provide the same viscosity characteristics. I had a GTI with oil-temperature and oil-pressure gauges for a while, and it was very informative to watch the relationship between engine temp, engine speed, oil temp, and oil pressure (as well as the huge range of oil pressure that was within acceptable limits).

 

[DanoT]

Synthetic often has a higher cook point, as well (i.e. can reach a higher temp while still performing within specifications),

Synthetic oil also has a lower pour temperature which means it doesn't thicken up as the temp drops as much as mineral oil, making synthetic oil ideal for northern climates when a block heater cannot be plugged in.