Thick oil, thin oil piston wear

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There are several articles on this website, and there are a multitude of posts saying the same thing, that lighter multigrade oils (0w20 0w30 etc) are better for car engines. These oils advertise efficiency as a selling point. I'm guessing they say the lower fluid friction will lower the internal resistance of the engine.

Even though the 0w20 oil has excellent starting viscosity My worry is that there could be a cooresponding increase in piston wear.

Each of us has our own opinions, and mine is that as far as piston wear, higher viscosity oils will do much better at the keeping the surfaces of the piston/rings and cylinder separated than low viscosity oil.

Comments, counterpoints?
 
K.
So you feel thicker oil is better for the rings. Fair enough. Find all the engines running 20 grades that burn oil past the rings and let's compare the mileages vs those same engines somewhere else in the world where thicker oil is specified and let's compare typical miles vs oil consumption where it's the rings that are at fault.
At start up all oil is too thick,so the rings in the cylinders are riding on the oil from the previous run cycle. As the oil warms the cylinders get splashed and lubricated.
Now since thinner oil will splash faster which is better.
Sure thicker oil will protect better at elevated oil temps but how many daily drivers operate at these elevated oil temps where a 20 grade may fail.
Consider the operation of the engine,the speeds at which it will be operated at then choose a viscosity that fits the driving conditions.
I'm not a thinner is better guy either. I run 40 grades in the summer because I drive my cars hard,and 20 grades in the winter. Regardless of what the oil cap says.
 
Last edited:
Originally Posted By: r2800
There are several articles on this website, and there are a multitude of posts saying the same thing, that lighter multigrade oils (0w20 0w30 etc) are better for car engines. These oils advertise efficiency as a selling point. I'm guessing they say the lower fluid friction will lower the internal resistance of the engine.

Even though the 0w20 oil has excellent starting viscosity My worry is that there could be a cooresponding increase in piston wear.

Each of us has our own opinions, and mine is that as far as piston wear, higher viscosity oils will do much better at the keeping the surfaces of the piston/rings and cylinder separated than low viscosity oil.

Comments, counterpoints?


I have read the oil university, read a lot of threads regarding lower oil viscosity and understand everything and kind of agree with all the points and yet our van got to 475K. with a diet of Mobil 1 5W50 for 300K and the last 20K on 30 and the engine didn't like it, the unibody rusted out to the point of cracking but the engine ran perfectly I looked for a replacement body anywhere I could couldn't find one in decent shape; my point is even agreeing with the theory the facts don't support it at least in my personal experience and yes I have used thick oil all my life until this small test, I might try again but with a grain of salt.
 
Where did you find M1 5W-50?
That's a grade of M1 that you don't typically find in the US.
Also, when you say that the engine "didn't like" a 30 what did you mean?
20W20 was the standard grade for a number of years before multigrade oils became widely available.
Honda and Ford both began recommending twenty grades more than a decade ago.
Millions of engines have been operated for billions of miles since with no indication that a twenty grade is too thin to protect the piston skirts, rings or any other part of any engine.
 
Everybody wants to jump a grade. If you do your homework, you can stay in grade and experiment using HTHS. You can adjust from 3.0 - 3.6. M1 0W-40 is 3.8
 
Since I'm learning more about engine oil, I'll probably start running a 0w30 in my Subaru during the winter and switch to a 0w40 in the summer. I frequently drive through some pretty steep long hills, and it can get pretty warm here in the summer.

It's kind of ironic that Fairbanks can be a frozen nightmare in winter, and approach 90F in the summer. I guess that makes proper oil selection for my car that much more important.
 
I challenge the next person who says "optimal" wrt viscosity, to qualify it.
What are you talking about? What's not optimal? Wear protection? Fuel consumption? Is it your prime concern to ensure that extra tenth of a MPG in the first minute of driving? It is for automakers, and their CAFE, but is that what you yourself are trying to optimize? How about flow? Is it flow? What are the consequences of flow speeds on a warming engine?

Oil X isn't the optimal viscosity. Automobiles are not the optimal mode of personal transportation. The ICE is not the optimal engine for the not optimal automobile running a non optimal viscosity. Any and everything is not optimal in some regard; we absolutely have to qualify it though, for it to mean something other than an abstraction.

As usual the viscosity issue takes the form of religious jihad; fears are being manufactured, and subsequently blown way out of proportion, supported by nothing but imaginations.
crazy2.gif

And no end is in sight. Tomorrow, there will be another thread "does 0w20 really protect anything?" and "does anyone still use motor oil grades from the cretaceous period? so old, must be horrible, made for pterydactyls" etc etc

It's one thing to stay on top of tribological evolutions, and equally critical to be aware of the driving forces and intentions behind the chemistries. Base stocks and the blends thereof have skyrocketed in oxidation stability, purity (or lack of undesirable contaminants if "purity" sounds too hokey for you) VI, and volatility. PMA polymeric VIIs have become further optimized for stability at common engine temps by molecular shape and length. But all that means in today's common formula is that they can push the boundaries of viscosity even further, optimizing them for VI/(CA)FE performance, while still maintaining the same or slightly improved stability of the outgoing product.

That's cool.

Except I don't care about CAFE. I don't want those boundaries pushed. I don't care about fractions of a percent increase in fuel economy/reduction of drag for the first ~4 minutes of engine operation. I really don't. They're not going to give me an extra 5MPG per tank.

What I do care about is benefiting from skyrocketed quality of the new bases, without re-trading some of that cleanliness and stability back for more VI, when I don't need it.
And I'm thankful that this can be had, by choosing grades of oil made with these new fantastic base oil blends, that haven't been pushed right to the edge of VI/FE performance. I'm talking about the 5w20s, 10w30s, 15w40s and straight grades made with GrIII+ ... and sure if i was taking a road trip, you bet your balls I'd consider buying a jug of quality GrIII+/IV/V SAE20 or SAE30 (AMSOIL for example)- as long as it's made with the same bases that carry the same uprated stability as it's peers within a product line. I like margins of protection and free moving piston rings.

If a 0w20 product of the same line uses even more stable base stocks (to make it perform suitably/per manufacturers spec) then I would gladly pick that product up- and because it would be needed (cold season) but not VI for VI's sake. I always maintain that there is no free lunch with motor oil. There is no motor oil that will satisfy CAFE and a brutal track day and do both optimally. But those are the demands I put on MY car. Maybe you drive much more sedately and couldn't care less/don't know/care about ring pack coking, volatility consumption, temporary/permanent shear-- but I do and passionately so, and will continue to investigate each oil's formulation to find the best one for the benefits that I want. Specs won't tell me that, that's why I'm here!
 
Originally Posted By: r2800

Each of us has our own opinions, and mine is that as far as piston wear, higher viscosity oils will do much better at the keeping the surfaces of the piston/rings and cylinder separated than low viscosity oil.


I agree. I tend to obsess over aluminum numbers in the Jeep 4.0 as the piston skirts are the chronic weak point in the last generation of that engine. Thicker oils tend to have little to no perceptible effect on iron (which is what people tend to focus on) but they seem to definitely lower the aluminum ppm's. Good enough for me, I run thick.

I only wish I'd have figured that out 40k ago.
 
Originally Posted By: jrustles
I challenge the next person who says "optimal" wrt viscosity, to qualify it.


Heavier than alcohol but lighter than honey? After reading pages of your posts I come away empty. Try taking a hard stand on something once in awhile.

I thought the newer lower viscosity base stocks can float a bearing better than an equivalent heavier ie. more viscous outdated base stock. That's why the new 0W-20 oils work so well. It's maddening to me when, instead of recognizing and appreciating new technology the old crew blames the government and CAFE for their perceived ills.

It's a free country. Use an "old mans" oil if you wish.

If oil is maintained at a reasonable temperature with a properly sized oil cooler, there would never be any need for a 30,40,50 or 60 weight oil. A heavy oil is a crutch for an improper design.
 
Originally Posted By: turtlevette
Try taking a hard stand on something once in awhile.



What do you mean, like "you're either with us or with the terrorists" kinda stuff? Come on now!! I have a hard stance on being explicit, does that count?
 
I might be the minority here but I don't feel there's a one size fits all when it comes to engine oil. How the engine is operated,ambient temps as well as usage should all be considered when deciding on what grade oil is chosen.
A vehicle operated in the winter,short tripped and mainly acquires city miles will require something different than the same vehicle operated in the desert pulling a trailer.
For instance my charger gets 5w-20 in the winter for obvious reasons but once warmer ambient temps arrive I prefer a 0w-40 because I'll be driving it harder,oil temps will increase and stay elevated because of how I'm driving it.
A 5w-20 is fine at oil temps of 200f however at 260f I'm more comfortable with a 0w-40 in the sump.
I don't feel that one size does for all,maybe most,but not all
 
Originally Posted By: jrustles
What do you mean, like "you're either with us or with the terrorists" kinda stuff? Come on now!! I have a hard stance on being explicit, does that count?

He may not have been diplomatic about it, but part of the notion of an oil being "optimal" is the balancing act. The German cars may "like" a thicker oil, but one isn't going to run an SAE 40 in them, particularly as a grocery getter in North America. A Focus might "like" a 0w-20, but a really thin 0w-20 might not be best for standing on the accelerator around an oval track. That's not to say either option will blow up an engine, but optimal is, as we've heard many times, as thin as is possible and as thick as is necessary.

The difference between optimal and "not optimal" isn't 50% reduced gas mileage or 25% reduced longevity, either, at least in any sensible shift from specified grade.
 
Originally Posted By: turtlevette
I thought the newer lower viscosity base stocks can float a bearing better than an equivalent heavier ie. more viscous outdated base stock.


OK turtlevette, it's that time in every thread where I say...."prove it"...using science that thinner oil "floats" a bearing better.

It's maddening to you when people don't understand your science, so you can just up and prove it if you want.
 
Originally Posted By: turtlevette
Originally Posted By: jrustles
I challenge the next person who says "optimal" wrt viscosity, to qualify it.


Heavier than alcohol but lighter than honey? After reading pages of your posts I come away empty. Try taking a hard stand on something once in awhile.

I thought the newer lower viscosity base stocks can float a bearing better than an equivalent heavier ie. more viscous outdated base stock. That's why the new 0W-20 oils work so well. It's maddening to me when, instead of recognizing and appreciating new technology the old crew blames the government and CAFE for their perceived ills.

It's a free country. Use an "old mans" oil if you wish.

If oil is maintained at a reasonable temperature with a properly sized oil cooler, there would never be any need for a 30,40,50 or 60 weight oil. A heavy oil is a crutch for an improper design.
















K. I've gotta ask. How does thinner oil float a bearing better than its thicker counterpart all things being equal.
No need to dumb it down. I can keep up
 
This could be total ignorance, but I never felt comfortable using a 0w20 oil on its own without mixing something thicker. Traditionally if I use a 0 weight ill use a euro blend - 0w40. People make a big fuss about it but I'd rather have too much protection than too little
 
Originally Posted By: mene
I have read the oil university, read a lot of threads regarding lower oil viscosity and understand everything and kind of agree with all the points and yet our van got to 475K. with a diet of Mobil 1 5W50 for 300K and the last 20K on 30 and the engine didn't like it, the unibody rusted out to the point of cracking but the engine ran perfectly I looked for a replacement body anywhere I could couldn't find one in decent shape; my point is even agreeing with the theory the facts don't support it at least in my personal experience and yes I have used thick oil all my life until this small test, I might try again but with a grain of salt.


Thicker oil provides greater separation between the piston, rings and liner...period...and reduces the length of the swept area that is undergoing boundary/mixed lubrication.

However, given that maximum piston speed is mid stroke, there can be excessive drag mid stroke...which wastes energy, but can't be any more "protective" than having a thinner oil at that point in the stroke.
 
Originally Posted By: Clevy
I might be the minority here but I don't feel there's a one size fits all when it comes to engine oil. How the engine is operated,ambient temps as well as usage should all be considered when deciding on what grade oil is chosen.
A vehicle operated in the winter,short tripped and mainly acquires city miles will require something different than the same vehicle operated in the desert pulling a trailer.
For instance my charger gets 5w-20 in the winter for obvious reasons but once warmer ambient temps arrive I prefer a 0w-40 because I'll be driving it harder,oil temps will increase and stay elevated because of how I'm driving it.
A 5w-20 is fine at oil temps of 200f however at 260f I'm more comfortable with a 0w-40 in the sump.
I don't feel that one size does for all,maybe most,but not all


Sounds fair enough to me.
 
Yeah, I know it's a big ask when we are talking syrup, honey, sweet spot, floating, everyone knows etc.
 
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