Contour Enthusiasts Group Archives Forums Modifications General Mods Why would you use 0W30?

To add to the confusion, why would you want it to be really thin at startup? I know that you want it to flow a little better, but how much is too much? Almost all the diesel trucks that came to our shop for oilchange use 15w-40 oil, does that mean their engine are going to blowup? Also, if thinner oil is better, then why would they want the oil the thicken up as it reaches operating temperature? Synthetic oil doesn't get affected much by temperature to begin with, so what exactly are you benefiting from using Mobil 1 0W-30 instead of 5W-30 in winter? I mean it's synthetic oil, and they really don't get that much thicker when it's that cold out (heck, they're thinner than at operating temperature). I just don't understand all these confusion...

Well Airknight I'm no "oil expert" by any means, but if its real cold outside and you start your car wouldn't it make sense to have "0" weight at start up instead of "5" weight Besides, we are talking about sythetic here, which from what I've been told/learned is refined thinner than convential oils. That being said, maybe those guys with diesels should change over to a synthetic 10W40 grade which Mobil doesn't make. In the summer I'd run Mobil 1 15W50 in those diesels and let it ride

One thing about oils is that you want to use the LOWEST viscosity spread reasonable. There are more additives used to get from 0 at cold to 30 at op temp than 5 at cold to 30 at op temp. The more additives in the oil, the less its life is (except the oil that is designed for extended drain intervals - whole different ballgame).

What does this mean to us? Since we are all pretty religious about changing our oil when it is due, probably not much. If you're changing Mobil 1 at 3000 miles, it means nothing. But to be on the safe side, 0W30 should be used when the climate calls for it and then switched to 5W30 when appropriate (or 5W20 if you like, but its not for me).

How about that week a couple years ago we hit nearly -60C + windchill? That's what 0W30 is good for... didn't help my neighbor's car though, his door handle broke off in his hand! LOL! I just stayed home and told work to piss off.

Hey when its real cold, like -10 or colder, you better have the 0W30 in the ride. Because if you don't, its toooooo late by then :p

Still, why would you want the oil to be thinner before the engine is warmed up, and have them thicken up when the engine is at operating temperature?

From what I remember of my chemistry... since the oil is colder it will be harder to pour or pump/flow to all the parts of the engine when cold. So its setup to have a lower visc when cold to help it get to all the moving parts faster and provide protection. Once the engine is warmed up and the oil comes up in temp it is inhertingly easier to pour and flow, but starts to lose the ability to sheet out over the parts and protect them. So its setup to bulk its visc as the temp increases to provide the protection needed.

That make sense?

But to blow your mind.. look at the stats on AMSOIL 5w30 verse its 0w30. You'll notice that the 0 has a large four bearing wear number than the 5, when at 75C. Probably has something to do with the additives providing less protection.

Ray

My guess on thinner at cold, thicker at hot: the viscosities are tested at a standard condition, but actual viscosity in use is affected by temperature, pressure, shear forces, etc.

Viscosity is actually a very tricky property to measure. Search the internet for terms like thixotropic, shear thinning, Newtonian fluid and you should get a good explaination of all the different types of viscosity.

First off: Wind chill ony affects things that are already warm... like people's bodies. A cold car in -10F in NOT going to be any colder because the wind is blowing!!!
Then the oil is thinner seeming when it's hot and if it was a lower viscosity it would be even worse. The 5W-20 is fine as someone said if you never run your engine very hard. I would NOT do it in an SVT. The 0W-30 as was said has a 'wider' span than 5W-30 and that does need more "stuff" in it to make it span that gap... so a little less of the oil is really oil... not much to worry about though. The "0" is only at startup, and doesn't matter too much... And yeah, viscosity is really a very complex issue, that is part of why it's said: use what is recommended by the manufacturer!!!! and do NOT use 10W-40 (unless you live in Death Valley... then it MIGHT be ok)

Motor Oil does NOT thicken when heated. Indeed it thins out. A better motor oil only resists it's propensity to thin. Thus, it is never thinner at 20 degrees F as it is at 200.
A temperature v. viscosity relationship for an oil is a downward sloping line.
The weight rating is actually a range of viscosities and not an exact number.
The W or winter weight viscosity is on a different scale than the second number.
Also, gear oils use a different scale. I believe 90W gear oil is the same viscosity as 50W motor oil.
Will try and dig out graphs to make sense of this.