CCS and MRV values for winter starts?

[Pesca]

Hi,

I have been told on this forum not to look only at the static viscosities to determine if the oil runs better at cold starts but more at the pumpability of the oil (dynamic viscositity) which, from what I undertsood, is demonstrated with the Cold Cranking Start (CCS) and Mini Rotary Viscometer (MRV) values.

My problem is I have a hard time interpreting this value, therefore I need some help.

For the CCS value, I read on the Amsoil website that for a determined viscosity, the oil has to stay below a defined value to be called 5w for example. In my understanding, that means that a lower value means a better oil for cold starts: Am I right?

Unfortenately, I couldn't find any information on the MRV value, so is it the same as the CCS one? The lower the better.

Last point to clarify my mind: Comparing two oils trying to find which one is better at cold starts (assuming that the "the lower the better" rule applies to both values), if one has a lower CCS value than the other but the higher MRV value, which one of the values is more important to make the choice?

On this thread, I am only talking about the cold start characteristics of the oil, not the quality of the oil concerning engine wear, TBN retention, additive package, etc...

Thanks for your inputs.

 

[JAG]

Yes lower is better for both for cold starts. CCS is for ease of cranking (the engine "turning" over). MRV is ease of pumping the oil. The limits on each have been developed to make sure the MRV limit is low enough that if the engine does turn over, it will definitely pump the oil; otherwise the engine may turn over, not pump enough oil and the engine possibly dies of lubrication starvation.

I would not bother with making a judgement between two oils based on the one having a lower CCS but a higher MRV. But if you really want to, I think it is better to have a lower MRV from an oil flow standpoint while a lower CCS may allow less fuel consumption in the first few minutes of really cold starts.

 

[Pesca]

Another question:

When I look at the Schaeffer oils numbers, there are average for the CCS values but really not that good for the MRV ones. Do they use a different test for the MRV?

For example: Compare to Pennzoil Platinum 5w30 with CCS at 4410cP and MRV at 6600cP, Schaeffer 7000 5w30 have 5610cP for CCS and 22400cP for MRV.

The only difference that I notice is that Schaeffer wrote the value as MRV TP1 and not just MRV. Does the TP1 make the difference?

Any Guess?

 

[JAG]

It appears based on my searching the TP1 refers to a specific cooling cycle. Without more searching I cannot answer your question but here is some reading that my help you answer it yourself: http://books.google.com/books?id=dw9RPjY...result#PPA93,M1

Also, just Google "MRV TP1" if the above does not fully help you.

 

[Pesca]

Did exactly what you did (may be should I have mentioned that in my previous post

), the google search resulting in that reading.
But doesn't give too much more information, it said it is still the ATSM D4684 test, that is why I posted.

May be to reformulate my question differently: Are there several MRV tests under the ATSM D4684 norm?

The fact that the other manufacturers don't put the TP1 mention doesn't mean that they use a different test method (thought it was normalized tests).

 

[TallPaul]

Problem with MRV and CCS is that they test at different temperatures for different "w" numbers. Somewhere on this site many years ago someone suggested or said that a tough and dirty way to compare is to double the MRV or CCS number for every 5 degrees drop in test value. I don't know. The one advantage of cold cranking is you can directly compare actoss "w" numbers.

 

[mechtech2]

Without testing, us the lowest first number for multi viscosity oils that you can. It is our best most reasonable shot at things.