A 5W is not a 5W is not a 5W

[Titan]

Originally Posted By: Jax_RX8
^^^^^^^^ Very well put and exactly the point I was trying to make.


I agree! Very nicely put.

 

[bob_ninja]

Thanks.

For my part these days I look at CCS/MRV/40C viscosity instead of the xxW number. I am finding that many 5Ws are sufficiently thin for cold startup.
Also, I tend to mix in some 5W20s as opposed to chasing 0W30s
I find it easier to get thinner oil from conventional 5W20 then expensive 0W30 synths.
Of course, in Canada we have colder temps, so downgrading to 20s makes sense.

 

[Audi Junkie]

Before I read and digest this whole post, I just want to say the forum needs some good viscosity comparison charts to compare common grades. We're supposed to be experts here and lack that basic tool. It'll be good for teaching as well as learning too.
Most charts I've seen are too flat, with the lines all converging too soon. They need to be log-scaled with good graphics. Can someone produce them???

 

[Audi Junkie]

Just to be helpfull and short, the various W ratings are done at a corresponding lower temp, -20f, -25f, -30f and such. The amount of visc "resistance" to the mini visc test thingy is progressively higher *within* the various grades. That is: 10w30 is thinner than 10w-40.

The max visc limit at lowered temp for 5w-20 is less than a 5w30 and that is thinner than a 5w-40. So, a conventional 10w30 could easily be thinner than a 5w-40 synthetic at the rather hot temp of +40C. Other anomalies arise too, such as some 5w30s being thinner than some 0w-30s at cool/cold temps.

 

[JohnBrowning]

It is not misleading at all. It clearly tells you that at -30°F this oil is bellow 7000 centistrokes of resistance to rotaional force etc.... So if you need to run a 5W oil for cold weather performance in most case's it will not matter if it is a 5W30 or 5W40 you will be able to safely start your car down to -30°F with out haveing to worry about anything. Case in point I used Redline 5W40 one winter and it soaked one night down to -30°F when I got up to go to church it was between -25° and -28°F depending on which weather program you where listening too. My little Toyota 2.4L turned over just like it normaly does and did not have any valvetrain noise or anything.Why? Because it wasa 5W rated oil. Now sure if you are in artic conditions on a regular basis would finding an oil witht he lowest CCS rateing be helpful????Maybe!

 

[bob_ninja]

I think it is -30C as opposed to F.
In any case, John you are still missing the point. That particular information about -30C is what most people *DON'T CARE ABOUT*
So why is it so prominently displayed on every bottle?

How many mornings during a winter temperature drops to -30C (-22F)? In my case, maybe few days, 5 max. That is in Canada too.

Say about 120 winter days, that is 5/120 = 4% of the time max

Now consider a more typical winter temperature of about say -10C / 14F. This would be typical on most mornings, so about 50% of the time.

Furthermore, I don't really care if my car will start at those extreme cold temps. Of course it will. Engines today are much more sophisticated, so [censored] right it will start. I am far more interested in minimizing damage taking place on cold startup.

So the real question of interest:

50% of the time (-10C / 14F) during winter how much damage (viscosity, thin/thick)

That is the question that the 1st number xxW should answer. That is what most are interested in.

Regarding starting, there are block heaters, there are bigger started/batteries, etc.