What temp does oil get "sludgey". Bad 4 car engine

[wowthisexists]

I think I run 0w-40 or 5w-40.
The oil in my trunk (spare quart) still seemed to be runny, at 5 degrees F.
So, it's ok to start a car engine at 5F ?
When does oil get so sticky that it's bad to start your car?

 

[tig1]

Originally Posted By: wowthisexists
I think I run 0w-40 or 5w-40.
The oil in my trunk (spare quart) still seemed to be runny, at 5 degrees F.
So, it's ok to start a car engine at 5F ?
When does oil get so sticky that it's bad to start your car?



Depends on the oil weight, brand of oil, dino or synthetic, etc.

 

[expat]

5F might be a bit to cold to start an engine........with a 20w-50


You will be just fine, but a block heater will help.

 

[abycat]

I start my engine in both vehicles at-40 with conventional 5w. The truck never gets plugged in but I try to with the car. Not always though.

 

[Shannow]

Try the SAE J300 table, and look at the low temperature pumping viscosity.

The grades are defined as a maximum viscosity at which it flows (the no shear means that the oil can't have any part lines - glugginess if you will). Industry and SAE have defined the viscosity as around 60,000 cP (cst are the same numers), so about 6,000 times as thick as hot oil.

Look at the chart, and you can see the temperatures that correspond to that viscosity for each of the "W".

5F is -15C, and a 20W would still pump without causing damage down to that temperature...your 5W is more than fine, and the 0W the best you can get....and note, these are the maximums, every oil has to be below the maximum (which makes TGMO a 5W by the look of it).

Note, that there's no test for how long it retains it's W rating when being run, so to be safe I'd choose a W rating that's applicable to your region's "worst day".

 

[eljefino]

Generally "sludge" is defined as irreversably wrecked oil that won't get out of its own way within your engine and needs to be removed with detergents or manually.

You are thining of generally thick oil in its natural cold state, that will return to its thin happy self when heated.

As you noticed with your shake test, 5'F ain't a thing. Look at all the cars around you running fine.

 

[zpinch]

Originally Posted By: tig1
Originally Posted By: wowthisexists
I think I run 0w-40 or 5w-40.
The oil in my trunk (spare quart) still seemed to be runny, at 5 degrees F.
So, it's ok to start a car engine at 5F ?
When does oil get so sticky that it's bad to start your car?



Depends on the oil weight, brand of oil, dino or synthetic, etc.


Please don't call it DINO OIL. Nothing to do with Barney.

About the sludge, it is normally defined as oxidized and consumed oil molecules clumped together in a larger mass that just makes a mess and makes for a bad day.

 

[Plumber]

I would call it jelly....and just as long as it is not SAE30 you should be fine!

 

[wowthisexists]

5W-40 is good to about -30F.
I will not be leaving the house at that point.
Seems like even 20-50 is good down to -4F.

Ok, so seems like 5* F is just fine for most oils.
Good to know. One less worry!

 

[Garak]

Originally Posted By: wowthisexists
5W-40 is good to about -30F.

It's fine colder than that, too, and I speak from experience.