Viscosity figures at different temps?

[BluEyes]

Hi all, new here and looking for some info...
I have been looking at the product data put out by the oil manufacturers, and can only find viscosity figures listed at 40*c and 100*c. So, what if I want to know the viscosity down at temps like 20, 0 and -20*C? The kind of range the oil will be when the car is started. Is there any way to find that out without testing it myself?

The main reason I ask is that I am trying to figure out what weight oil to use in my old Mercedes 220D (well, old car but recently fresh engine).
The owners manual says to use 30 weight oil in temps 32*F and above, 10 weight for 0*F to 32*F, and 5 weight below 0*F... Well, I'd rather run a multigrade synthetic than straight mineral oil, I'm kinda choosing between Mobil 1 5W40 and 15W50 and was looking to match up which had viscosity closest to Mercedes reccomendations during cold cranking conditions.

 

[Ken2]

Why not use a diesel engine oil? I'd use 5W-40 year 'round, or 15w40 summers and 5W-40 winters.

Mobil 1 Truck and SUV 5W-40 is a diesel engine oil, and 15W-50 is a gasoline engine oil, although suitable for light duty diesels like yours.


Ken

 

[Blake Sobiloff]

Someone posted a link to a Shell online calculator that will give you a rough idea of the information you're looking for. It is intended to help people blending different weights of oils determine what the viscosities will be, but it'll work for unblended oils, too. I bookmarked it, but I'm on the road with a different computer; maybe a search on this site will find it.

 

[Doug Hillary]

Hi,
BluEyes - Ken2 made a very good recommendation for all year round use - 5w-40!

For the oil he nominated and the temps you nominated, this "very rough calculation" may help you;
-20c = 6340cSt
0c = 1066cSt
20c = 282cSt

A suitably MB Approved and Listed 0w-40 oil would also perform very well in all year use

Regards
Doug

 

[Blake Sobiloff]

OK, I'm home again. Here's the URL to the Shell viscosity calculator: Shell toolbox

 

[TomJones76]

The cheap option would be Shell Rotella T Synthetic 5W40.
The expensive option would be Mobil 1 Truck and SUV.
The [unspeakably cheap for a fine Mercedes automobile such as yours, but perfectly safe] alternative option is Supertech 15W40 in the summer and Shell Rotella T Synthetic 5W40 in the cold months.
I've seen a couple of UOA from the 240D and 300D series of Mercedes Diesel, and for those engines the huge sump will most likely let you got 10-15,000 miles out of your oil before soot hits the condemnation limits.