Engine oil - mineral vs synthetic

[Rich Z]

Been reading a lot of stuff about engine oil lately, and I found this little quote to be right interesting in explaining the difference between mineral (dino) oil and synthetics.

The nitty gritty of oils. Mineral oil is refined and the refining process is pretty good but not perfect. here's how my friend from Redwood oil explained it to me so it was easy to understand. Crude oil has everything in it, from gasoline to diesel to all of the weights of oil and each part is processed out of the whole crude oil. Once a weight of oil has been refined. What they are doing to get the different weights is separating the different sizes of molecules that make-up the thickness of the oil. Oil molecules are like little ball bearings that let metal to metal parts glide on them between a certain clearance. Thin oil has small ball bearing like molecules and thicker oils have larger molecules. Picture a bag of marbles, where you have 100 individual marbles. Now instead of having all of the marbles the exact same size, imagine about 80% of the marbles being 1" in diameter and 10% being 3/4" in size and the remaining 10% being 1 1/8" in diameter. Now lay out all of the marbles on a flat surface and lay a piece of wood over the top of it. What is the board going to be riding on? The small percentage of the largest 1 1/8" marbles that are scattered out under the board. Well, that won't make the board very stable and it won't be riding on the majority of the 1" marbles like it is supposed to be doing until the biggest marbles have been made smaller in size so they ALL can carry the board smoothly and glide it across the surface of the ground. That is very much like refined oil. Refined oil has a high percentage of the correct size molecules, BUT, there is also a percentage of carry-over sizes that are smaller or larger in size as well. They can't refine it perfectly. Your engine bearings are like that piece of plywood, not riding smoothly on ALL of the marbles, only in the largest one's which makes the load surfaces uneven and smaller. Now imagine the same piece of plywood with the same 100 marbles, only this time, they are ALL exactly 1" in size, thus dispersing the load over the entire surface of the plywood and floor. That would be the ideal situation and this is very much like synthetic oil molecules, where the molecules are not refined and sorted-out by size but rather are MADE synthetically to a very specific size which carries more of a load and disperses the load over a greater surface area. That is why synthetic oils work so much better than refined oils. The only problem I have ever found with synthetic oils is if you don't have an oil leak with regular oil, you probably will once you go to synthetic. That stuff just has a way of finding its way out of your engine.

Source: http://www.badasscars.com/index.cfm/...102/prd102.htm

[shakedown067]

Nice little read! I find it funny that anyone that ever discusses synthetic oil always brings up that it leaks. Well, if it flows better, it's more likely to find the holes of seals breaking down sooner than later. To me, this is a good thing as I'd rather address aging gaskets/seals before they really deteriorate. Of course, you can always just go to a heavier weight synthetic and cure it as well, and just over look what's actually causing those leaks.

[Rich Z]

This link points to a gold mine of information concerning engine oils -> http://www.bobistheoilguy.com/motor-oil-101/

Chapter 5 was of particular interest to me.

[Kap142]

I have always used the Chevy recommended Mobil One. Never had a leak. Never had any consumption and LS6 purrs like a Z should. I'm a happy camper. My personal choice for all my two vehicles is synthetic. Just my choice but very cool read Rich.

[Rich Z]

Found another webpage with some interesting info concerning oils:

http://540ratblog.wordpress.com/2013...-test-ranking/

Of particular interest to me are the following statements:

THE BENEFITS OF USING THINNER OIL:

• Thinner oil flows quicker at cold start-up to begin lubricating critical engine components much more quickly than thicker oil can. Most engine wear takes place during cold start-up before oil flow can reach all the components. So, quicker flowing thinner oil will help reduce start-up engine wear, which is actually reducing wear overall.

• The more free flowing thinner oil at cold start-up, is also much less likely to cause the oil filter bypass to open up, compared to thicker oil. Of course if the bypass opened up, that would allow unfiltered oil to be pumped through the engine. The colder the ambient temperature, and the more rpm used when the engine is cold, the more important this becomes.

• Thinner oil also flows more at normal operating temperatures. And oil FLOW is lubrication, but oil pressure is NOT lubrication. Oil pressure is only a measurement of resistance to flow. Running thicker oil just to up the oil pressure is the wrong thing to do, because that only reduces oil flow/lubrication. Oil pressure in and of itself, is NOT what we are after.

• The more free flowing thinner oil will also drain back to the oil pan quicker than thicker oil. So, thinner oil can help maintain a higher oil level in the oil pan during operation, which keeps the oil pump pickup from possibly sucking air during braking and cornering.

• The old rule of thumb that we should have at least 10 psi for every 1,000 rpm is perfectly fine. Running thicker oil to achieve more pressure than that, will simply reduce oil flow for no good reason. It is best to run the thinnest oil we can, that will still maintain at least the rule of thumb oil pressure. And one of the benefits of running a high volume oil pump, is that it will allow us to enjoy all the benefits of running thinner oil, while still maintaining sufficient oil pressure. A high volume oil pump/thinner oil combo is preferred over running a standard volume oil pump/thicker oil combo. Because oil “flow” is our goal for ideal oiling, NOT simply high oil pressure.

• Oil flow is what carries heat away from internal engine components. Those engine components are DIRECTLY oil cooled, but only INdirectly water cooled. And better flowing thinner oil will keep critical engine components cooler because it carries heat away faster. If you run thicker oil than needed, you will drive up engine component temps. For example: Plain bearings, such as rod and main bearings are lubricated by oil flow, not by oil pressure. Oil pressure is NOT what keeps these parts separated. Oil pressure serves only to supply the oil to this interface. The parts are kept apart by the incompressible hydrodynamic liquid oil wedge that is formed as the liquid oil is pulled in between the spinning parts. As long as sufficient oil is supplied, no wear can occur. In addition to this, the flow of oil through the bearings is what cools them. Here are some comparison numbers from an 830 HP road race engine on the track:

15W50 oil = 80 psi = 265* oil sump temperature

5W20 oil = 65 psi = 240* oil sump temperature

Here you can see how the thicker oil flowed more slowly through the bearings, thus getting hotter, driving up bearing temperatures and increasing sump temperatures. And the thinner oil flowed more freely and quickly through the bearings, thus cooling and lubricating them better than thicker oil, while also reducing sump temperatures. If an engine is running hot, use a thinner oil to increase flow, increase internal component cooling, and help keep sump temperatures down. Keeping oil temps down is important to help keep oil below the threshold of thermal breakdown.

• Thinner oil will typically increase HP because of less viscous drag and reduced pumping losses, compared to thicker oils. That is why very serious Race efforts will generally use watery thin oils in their engines. But, an exception to this increase in HP would be in high rpm hydraulic lifter engines, where thinner oil can allow the lifters to malfunction at very high rpm. In everyday street vehicles, where fuel consumption is a consideration, thinner oils will also typically increase fuel economy. The majority of new cars sold in the U.S. now call for 5W20 specifically for increased fuel economy. And now Diesel trucks are increasingly calling for 5W30, also for fuel economy improvement.

• With the exception of high rpm hydraulic lifter engines, almost no engine should ever need to run oil thicker than a multi-viscosity 30 weight. The lower the first number cold viscosity rating, the better the cold flow. For example, 0W30 flows WAY better cold than 20W50. And 0W30 flows WAY better cold than straight 30wt, which is horrible for cold start-up flow and should be avoided at all cost. And the lower the second number hot viscosity rating, the better the hot flow. For example, 0W30 flows WAY better hot than 20W50.

• Thicker oil DOES NOT automatically provide better wear protection than thinner oils. Extensive “dynamic wear testing under load” of over 100 motor oils, has shown that the base oil and its additive package “as a whole”, is what determines an oil’s wear protection capability, NOT its viscosity. For example, some 5W20 oils have proven to provide OUTSTANDING wear protection, while some 15W50 oils have only been able to provide MODEST wear protection. So, do not run thicker oil under the false assumption that it can provide better wear protection for our engines.

BOTTOM LINE: Thinner oils are better for most engine lubrication needs.

[Rich Z]

Find myself reading about oil again, and found an interesting quote:

No. What I said was that engines designed and built for low viscosity lubricants have reinforced features and better technology that do extend the life of an engine. For instance, unlike the trimetal bearings of the past, low friction engines use AlPbSi bearings. These are a "harder" material that minimizes "flexing" and distribute bearing load/peak oil film pressure much more evenly. The alloy is also much more resistant to bearing seizure. The durability of this type of alloy is regarded by Mahle, Clevite, and others in the bearing industry to be long-lasting and capable of achieving 300k with minimal wear. Low friction engines also employ low-tension piston rings that minimize friction compared to older designs. Low viscosity lubricants work well with low-tension rings to bias the lubrication regime more toward hydrodynamic verses mixed/boundary. Film thickness is the primary factor for wear at the piston ring pack. Low viscosity lubricants provide a greater film thickness vs higher viscosity lubricants. As a consequence of the higher flow characteristics of lower viscosity lubricants there is lower cold-startup & operating wear because of lower ring tension.

Engines designed and built for lower viscosity oils are more durable than yesterday's engines because they are just better made, tighter manufacturing tolerances, better metallurgy, better bearings, etc. Is this technology and new hardware applicable to engines spec'd with higher viscosity oils? Yes. Will running a heavier weight oil in an engine designed for a 20wt lead to lower wear? No. Could it increase wear? Yes. Why? Because OEMs design their engines for oil flow characteristics for an operating range of 80C to 100C. This is where it is expected an engine will operate for the majority of its life. It is also the temperature range where lubricants provide their best protection and efficiency. So now you have the steady-state wear rate that is dependent mainly on film thickness (steady state is mainly hydrodynamic). When we talk about wear and engine durability, the primary component suject to the most wear and arguably the limiting factor for durability is the piston ring pack. Engineers design these for a flow rate to the ring lands to attain a target film thickness based on engine rpm (piston velocity/shear) and steady-state operating temperature. If piston/cylinder lubrication is "flooded" then there is increasee oil consumption. If it is "starved", then mix/boundary condition (increased wear rate). All oil channels are metered for an expected volume. Going too high a viscosity of oil in an engine designed for 20 wt will shorten engine life. How much more wear, I don't know. One thing is absolutely certain and well known by industry experts, nothing increases the wear rate of an engine (under normal operating conditions) than operating above 2500 rpm.

Every SAE published industry study on the subject of engine wear rates involve studying the effect of load and engine rpm on wear rate. In every instance, rpm below 2000 and full load (WOT) and oil sump temperatures as high as 130C did not change the wear rate. Above 2500 rpm for any viscosity oil, at ideal operating sump temperature, always increased the wear rate. It is increased anywhere from 2x up to 10x depending on rpm. This is because of increased shear rate. Main and rod bearings are far more tolerant than piston rings. Piston velocity, piston/cylinder temperature, and combustion chamber pressures increase dramatically when essentially racing an engine. Fortunately, everyday engines don't live at high rpms. Every engine has a finite life.

Source: http://www.bobistheoilguy.com/forums...pics/2710312/2

[LEJ ZO6]

The thing that has me sold on synthetic oil more than anything else is the temperature rating. Synthetic has a higher working limit than dinosaur oil.

[Rich Z]

From what I have been able to gather, the ONLY negative of synthetic oil is that it costs more than refined mineral oil. If you have an oil leak, it's not the fault of the oil you use, you have a bad seal or gasket somewhere that needs to be replaced. Using a thicker oil to stop an oil leak is being penny wise but dollar foolish.

[Rich Z]

This blog has been updated with some newer testing done.

https://540ratblog.wordpress.com/

I have to admit, the Quaker State Ultimate Durability looks pretty darn impressive!

[Cor66Vette]

Originally Posted by LEJ ZO6

The thing that has me sold on synthetic oil more than anything else is the temperature rating. Synthetic has a higher working limit than dinosaur oil.

On a similar note:

I saw an experiment performed where one sauce pan containing synthetic oil and another sauce pan containing regular oil were each put on a stove top flame at the same time. The regular oil bubbled pretty darn fast, whereas the synthetic oil held out.

Sold on synthetic after that.