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Thicker isn't Always Better

5.0Flareside

GingaNinja
14,464
384
La Vergne, TN
This is going to be a quick explaination on why, its ok to run a 0w20/30/40 in an older vehicle and why thicker is not better.

I've heard alot over past couple of years, "oh i aint gonna run no 5w30 instead of 10w30, that stuffs junk!" or "yeah right your crazy if you think im gonna run 5w20 in my truck, that stuff is like water!"

lets break down a 0w30. the 0w part of the multi-weight listing. The W stands for Winter. AKA cold flow rate. a 0w will ALWAYS FLOW BETTER than 5w, 10w, 15w etc. No if ands or buts about it. The weight designation is determined by Kinematic Viscosity. Which is basically the resistance to flow at a specific temperature. the only time the oil will act as a 0w is at cold start up, which will allow it to protect better at start ups. now on a engine with leaky valve seals, it may cause some start up smoke, but thats only due to the leaky valve seals, not the oil. Oils never cause smoking or leaks, they only expose them.

Now when people think that a 0w30 is to thin for my engine that calls for a 10w30, thats absurd. as said above the 0w is only noticable at cold starts. the oil will be the same viscosity at opperating temp as a 10w30, which is where the engine will be at the majority of its life. By using a thinner cold flow oil, your just protecting the engine better at startup.

The W viscosities are tested and determined at 40*C. the opperating temp, the 30 in 0w30, are determined at 100*C. These tests are of the Kinematic Viscosity of the oil at those temperatures. then they have a scale and the place the rating on the oil.


Now down to why people think a 15w40 is better than a 0/5/10w30 oil in an engine calling for the 30. Its a VERY old school way of thinking. back in the 70's lots of people thought thicker is better. makes everything quieter so it must be lubricating it better. Back then this may have very well been true. but my oh my... 40 years has definitely changed oils. But people are still thinking the same way lots of times.

People want that extra 5lbs of oil pressure to make them feel good. when in reality, they may be doing more harm than good. Extra oil pressure just means the oil is having to work harder to get into areas between bearings, in lifters, through pushrods, and back down again. this is putting more strain on a oil pump. thus causing more drag through the entire system. Heck you can see a couple pounds of oil pressure drop by going from a conventional oil to a Synthetic, simply due to the fact of the way the Synthetics are much better at reducing friction due the molecular make-up of them.


Im sure i may have missed something, if so ask it... im tired.. and going to bed now.. lol.
 

mrxlh

Oilfield Trash
5,904
430
Stigler, OK
Still negates the fact the the clearances in the engine were designed around a specific weight of oil. Whatever the filler cap specifies, (grade and weight) trumps anyone here on this boards credentials, unless you are a PE and have designed a production engine.
 

5.0Flareside

GingaNinja
14,464
384
La Vergne, TN
Still negates the fact the the clearances in the engine were designed around a specific weight of oil. Whatever the filler cap specifies, (grade and weight) trumps anyone here on this boards credentials, unless you are a PE and have designed a production engine.

Yeah. But you can run a 0w30 and never have a issue due to clearances etc. This thread is aimed at people wondering if it's ok to run a 0w oil. Which it's perfectly ok. And engine will never know except much improved start up protection and continued like stock at operating temp protection..
 

mrxlh

Oilfield Trash
5,904
430
Stigler, OK
Yeah. But you can run a 0w30 and never have a issue due to clearances etc. This thread is aimed at people wondering if it's ok to run a 0w oil. Which it's perfectly ok. And engine will never know except much improved start up protection and continued like stock at operating temp protection..
I would not run a zero weight oil in anything that was not designed around zero weight. 85% of wear happens on startup, 10% happens at the "critical" the remaining 5% happens at thermal transition and or normal wear. The only reason zero weights were designed, were behind tighter geometrical tolerances, not greater tolerances. Ability to flow cold is one thing, shear, wedge thickness, surface area, and cavitation are entirely different animals. Leave out heat rejection calculations and you are shooting in the dark.
 

BuzzGun79

Nov.TOTM 2012 / 2012 TOTY
2,388
55
Still negates the fact the the clearances in the engine were designed around a specific weight of oil. Whatever the filler cap specifies, (grade and weight) trumps anyone here on this boards credentials, unless you are a PE and have designed a production engine.

I would not run a zero weight oil in anything that was not designed around zero weight. 85% of wear happens on startup, 10% happens at the "critical" the remaining 5% happens at thermal transition and or normal wear. The only reason zero weights were designed, were behind tighter geometrical tolerances, not greater tolerances. Ability to flow cold is one thing, shear, wedge thickness, surface area, and cavitation are entirely different animals. Leave out heat rejection calculations and you are shooting in the dark.

Lester makes some very key valid points here.....through my own experiences and knowledge...I have to agree...
 

5.0Flareside

GingaNinja
14,464
384
La Vergne, TN
He does make some key points. But the oil will still retain characteristics of all it's additive and chemical makeup film strength, anti wear additives Etc even when it's a cold start up it's just simply thicker. And a can't say that ya know for sure 85% of wear happens in start up. Simply no way to 100% know that. But a lot of it does. But with better film strength and metal penatration of an oil, it'll leave a nice coating on everything to protect it better. All of which can happen with a quality oil. So by using a 0w it thins the oil back out a small bit allows it to flow, and get between metals quicker. It's not magically not got any characteristics of its standard operating temp.
 

SuperCab

Moderator
Staff member
10,067
543
Montana
Will a 0w30 shear quicker than a 10w30? I always heard the larger the jump in viscosity the quicker the oil would "wear out"... That is the viscosity indexers would no longer do their job and you'd be left with about a 15 or 20 weight oil in this case. Maybe it's not such an issue with the modern synthetics?
 

5.0Flareside

GingaNinja
14,464
384
La Vergne, TN
Some do some don't. That's due the viscosity index improvers. But a more quality base stock G-IV/G-V won't need as many VII's and thus will be much less likely to shear to a thinner weight.

The shear issue is the key reason why many people suggest running a robust 10w30(south) or 0w30 (north) in the Shelby's that call for a 5w50 full syn motorcraft. I've seen UOA that show the 5w50 shear down to a 30 after around 3k miles. It simply isn't needed unless seeing lots of track time.

I'll show my used oil analysis on my 0w30 in my truck that I beat the ever living crap out of.. And show how it barely shears if any at all when I ge another 1k or so on it.. Bearing 3k on this fill so far, getting close to 7k on engine
 

mrxlh

Oilfield Trash
5,904
430
Stigler, OK
He does make some key points. But the oil will still retain characteristics of all it's additive and chemical makeup film strength, anti wear additives Etc even when it's a cold start up it's just simply thicker. And a can't say that ya know for sure 85% of wear happens in start up. Simply no way to 100% know that. But a lot of it does. But with better film strength and metal penatration of an oil, it'll leave a nice coating on everything to protect it better. All of which can happen with a quality oil. So by using a 0w it thins the oil back out a small bit allows it to flow, and get between metals quicker. It's not magically not got any characteristics of its standard operating temp.

You don't have to believe me, but you had better believe the Engineers designing todays engines. If you have a larger clearance between the bearings and the crank, crank and rods, a zero weight oil will have less protection at startup, due to not being to take up the clearance void. The clearance tolerance is directly related to the film thickness of a particular oil, simply because automotive engines do not prelube before start. This is a very fine line between making it 250k and 100k. The tighter the clearances the longer the engine lasts. Look a the clearances of a engine requiring 5W oils and that of the latest engines speced for 0W. The clearances are are reduced in most cases by half, some even more.

A 0w has wonderful film strength at a clearance of .0015" but terrible at a clearance of .005" On the first compression stroke without oil pressure present the 0w will have far less wedge cushion than that of a 5w or 10w, it is math and physical properties of the lube oil, no amount of marketing or opinions can change the actual facts.
 

73F100Shortbed

That's how we roll!
5,937
320
NJ
Don't try explaining this to a woman. They'll always say thicker is better :rolling laugh:

(This post brought to you by the fact that FTF said I hadn't posted anything in awhile)
 
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