Motor Oils - An Explanation

[dsp26]

The SAE is the Society of Automotive Engineers. The SAE classifies motor oils according to certain viscosities and very general temperature ranges at which they can be used. Automobile and equipment manufacturers also specify which oil should be used for a particular ambient temperature operation. It is important to note that the viscosity and temperature range values listed by automobile and equipment manufacturers are almost always meant for petroleum oil. The same viscosity oil in a premium quality synthetic will have drastically lower cold temperature flow and operation properties as well as drastically higher high temperature operational properties. This is very important to remember this when determining which oil to use in a specific application and ambient temperature or range of temperatures expected to be encountered.

Today, most automobiles and trucks use multi-viscosity oils. Multi-viscosity petroleum oils are manufactured by starting with a lower viscosity base stock oil and blending in Viscosity Index Improvers (VI’s). The purpose of the VI’s are to allow a lower viscosity oil, such as a SAE 10W oil to flow like a 10W oil at low ambient temperatures (such as during cold starting) and also flow like a SAE 30W oil at higher ambient and operating temperatures. The resultant formulation is called a multi-viscosity oil, and in this example, would be called a SAE 10W-30.



Okay... The long, but simpler explanation.

Oil is naturally monograde. It has one viscosity at any particular temperature, and it thins and thickens predictably as temperature goes up and down.

So let's just say we have an oil that's has a magic viscosity of "10" at 0 degrees celcius.

By definition, we call this oil "10W".

Let's just say we have another oil that has a magic viscosity of a much thicker "50" at 0 degrees celcius.

By definition, we'll call this oil "50W".

If we heat up both oils up to 80 degrees celcius (about the right temp for an engine), both oils will get much much thinner.

Now here comes the crux of the problem. The 10W might be a perfect viscosity when it's 0 degrees. It covers the parts nicely and flows nicely. But when it gets to 80 degrees, the oil is too thin.

The 50W might be a perfect viscosity when it's 80 degrees. It flows nicely, and has a nice thick film over the parts. But when it's 0 degrees, it's too thick to pump.

So what's the solution? Well, take a 10W grade oil, and add synthetic polymers. These polymers have a unusual kind of ability to "stretch" when heated, making the oil thicker, but "contract" when cold, so they don't affect the viscosity of the oil.

So when the oil is at 0 degrees, the oil acts like it's a 10W oil. When it gets hot, the polymers "stretch", and the oil thins, but the polymers inside them thicker, meaning that it doesn't thin as much as it would normally. It might be about as thin as say, a 50W oil at 80 degrees.

In this case, you would call the oil a 10W-50, because it acts like a 10W oil when cold, but acts like a 50W oil when hot.


http://img.photobucket.com/albums/v281/dsp26/Maintenance/SR20OilViscoscity.jpg


Search Keyword: Oil Viscosity, Ambient, Engine, Temperature

[dsp26]

^^^i take no credit for the above info and rightfully quoted the person teaching it...

[Mr_will]

so would it be fair to say that its not always the case that a lower cold viscocity is better?

ie especially in australia where it really doesnt get THAT cold, would say a 10w 30 be better than a 5w 30?

[Limbo]

yes your right. Usually you ar supose to determine the heat range. But i think honda Australia take this into account when they make the cars and oils.

Rem some cars produce more heat. Generally smaller engine do not produce as much heat, and on your higher reving ones that produce enough heat they put an oil cooler.

Also another point you have a raidatior to supplement your cooling & heating which will react faster than oil and it has a thermostat to help.

ALso some 10w30 have a higher heat tolerance, i.e Mobile 1 ELF, Redline, Castrol R.

Oils ain't oils, ;)

[Mr_will]

Also i have a oil stability analysis which i downloaded. Its a large PDF but it shows you which oils breakdown faster and how well they protect after 5,000 km or miles i forgot. It test a very wide range of oils and even oils we can't get it AUst! If there is enough interest i'll upload it somewhere


definately would like to see it!

i'm driving a da9, and when i go to buy oils there seem to be a few that are designed for "older engines" but theyre always a fair bit cheaper than say formula r (now castrol edge), and im never sure whether to go with a higher quality oil or one designed for older engines

[Limbo]

Here a good read for you guys out there

Myth #1: Synthetic motor oils damage seals.

Untrue. It would be foolhardy for lubricant manufacturers to build a product that is incompatible with seals. The composition of seals presents problems that both petroleum oils and synthetics must overcome. Made from elastomers, seals are inherently difficult to standardize.

Ultimately it is the additive mix in oil that counts. Additives to control seal swell, shrinkage and hardening are required, whether it be a synthetic or petroleum product that is being produced.

Myth #2: Synthetics are too thin to stay in the engine.

Untrue. In order for a lubricant to be classified in any SAE grade (10W-30, 10W-40, etc.) it has to meet certain guidelines with regard to viscosity ("thickness").

For example, it makes no difference whether it's 10W-40 petroleum or 10W-40 synthetic, at -25 degrees centigrade (-13F) and 100 degrees centigrade (212 degrees F) the oil has to maintain a standardized viscosity or it can't be rated a 10W-40.

Myth #3: Synthetics cause cars to use more oil.

Untrue. Synthetic motor oils are intended for use in mechanically sound engines, that is, engines that don't leak. In such engines, oil consumption will actually be reduced. First, because of the lower volatility of synlubes. Second, because of the better sealing characteristics between piston rings and cylinder walls. And finally, because of the superior oxidation stability (i.e. resistance of synthetics against reacting with oxygen at high temperatures.)

Myth #4: Synthetic lubricants are not compatible with petroleum.

Untrue. The synthesized hydrocarbons, polyalphaolefins, diesters and other materials that form the base stocks of high-quality name brand synthetics are fully compatible with petroleum oils. In the old days, some companies used ingredients that were not compatible, causing quality synlubes to suffer a bum rap. Fortunately, those days are long gone.

Compatibility is something to keep in mind, however, whether using petroleum oils or synthetics. It is usually best to use the same oil for topping off that you have been running in the engine. That is, it is preferable to not mix your oils, even if it is Valvoline or Quaker State you are using. The reason is this: the functions of additives blended for specific characteristics can be offset when oils with different additive packages are put together. For optimal performance, it is better to use the same oil throughout.

Myth #5: Synthetic lubricants are not readily available.

Untrue. This may have been the case two decades ago when AMSOIL and Mobil 1 were the only real choices, but today nearly every major oil company has added a synthetic product to their lines. This in itself is a testament to the value synthetics offer.http://www.motorpoint.com.au/images/go_top.gif (http://www.motorpoint.com.au/syntheticlubrication.asp#top)

Myth #6: Synthetic lubricants produce sludge.

Untrue. In point of fact, synthetic motor oils are more sludge resistant than their petroleum counterparts, resisting the effects of high temperature and oxidation. In the presence of high temperatures, two things can happen. First, an oil's lighter ingredients boil off, making the oil thicker. Second, many of the complex chemicals found naturally in petroleum base stocks begin to react with each other, forming sludge, gum and varnish. One result is a loss of fluidity at low temperatures, slowing the timely flow of oil to the engine for vital component protection.

Further negative effects of thickened oil include the restriction of oil flow into critical areas, greater wear and loss of fuel economy.

Because of their higher flash points, and their ability to withstand evaporation loss and oxidation, synthetics are much more resistant to sludge development.

Two other causes of sludge -- ingested dirt and water dilution -- can be a problem in any kind of oil, whether petroleum or synthetic. These are problems with the air filtration system and the cooling system respectively, not the oil.

Myth #7: Synthetics can't be used with catalytic converters or oxygen sensors.

Untrue. There is no difference between synthetic and petroleum oils in regards to these components. Both synthetic and petroleum motor oils are similar compounds and neither is damaging to catalytic converters or oxygen sensors. In fact, because engines tend to run cleaner with synthetics, sensors and emission control systems run more efficiently and with less contamination.

Myth#8: Synthetics void warranties.

Untrue. Major engine manufacturers specifically recommend the use of synthetic lubricants. In point of fact, increasing numbers of high performance cars are arriving on showroom floors with synthetic motor oils as factory fill.

New vehicle warranties are based upon the use of oils meeting specific API Service Classifications (for example, SJ/CF). Synthetic lubricants which meet current API Service requirements are perfectly suited for use in any vehicle without affecting the validity of the new car warranty.

In point of fact, in the twenty-eight years that AMSOIL Synthetic Lubricants have been used in extended service situations, over billions of miles of actual driving, these oils have not been faulted once for voiding an automaker's warranty.

Myth #9: Synthetics last forever.

Untrue. Although some experts feel that synthetic base stocks themselves can be used forever, it is well known that eventually the additives will falter and cause the oil to require changing. Moisture, fuel dillution, and the by-products of combustion (acids and soot) tend to use up additives in an oil, allowing degradation to occur.

However, by "topping off", additives can be replenished. Through good filtration and periodic oil analysis, synthetic engine oils protect an engine for lengths of time far beyond the capability of non-synthetics.

Myth #10: Synthetics are too expensive.

Untrue. Tests and experience have proven that synthetics can greatly extend drain intervals, provide better fuel economy, reduce engine wear and enable vehicles to operate with greater reliability. This more than offsets initial price differences. All these elements combine to make synthetic engine oils more economical than conventional non-synthetics.

In Europe, synthetics have enjoyed increasing acceptance as car buyers look first to performance and long term value rather than initial price. As more sophisticated technology places greater demands on today's motor oils, we will no doubt see an increasing re-evaluation of oil buying habits in this country as well.

CONCLUSIONS

Since their inception, manufacturers of synthetic motor oils have sought to educate the public about the facts regarding synthetics, and the need for consumers to make their lubrication purchasing decisions based on quality rather than price. As was the case with microwave ovens or electric lights, a highly technological improvement must often overcome a fair amount of public skepticism and consumer inertia before it is embraced by the general population.

But the word is getting out as a growing number of motorists worldwide experience the benefits of synthetic lubrication. The wave of the future, in auto lubes, is well under way.

[Limbo]

http://bestsyntheticoil.com/amsoil/technical-data-bulletins/Specs-June-17-2003.pdf

ok i lost the file but i found the link for it. Have a look

[Limbo]

Ok i have a fuller and more uptodate version of that file if someone re info.
The one above is 25pages. I have the 150page one that i have now found.

it discusses the oils rather than just give you the tables. PM me with your email addy if you want it

[dsp26]

^^^yes please dsp_26@hotmail.com thanks!!!


but yes depending on which part of Australia you are you have to get the right viscosity for the right season also if your that pedantic with servicing (which we should). i personally will never switch from 5 or 10w30 only because response improvement is so noticable over a 10w40.

the above quotes in the original post came about from another discussion when argument brewed over what was better... obviously it was different for QLD/NSW/VIC...

Honda would've taken this into account but like Nissan (who formulates 7.5w30) it is a general formulation to cater for ALL Australia and not on a state basis as it would then provide too small a market and less gain for them...

[dsp26]

also about heat generation Limbo is also right... BUT i doubt very much your average S/XR6/VRX/Camry V6 would create more heat than a high revving, high CR Type-R motor...

[aaronng]

Guys, please include the link from which you copied and pasted the info from. Edit your posts above.

[Limbo]

Arronng i forgot where i got it from sorry mate. It was off a search i did but i can't find it now. It was from Amsoil's CEO or something, someone high up from that company

P.S i'm gonna try and get my hands on some amsoil just fround a place in Melb that has them now. We'll see how she goes apparently its better than mobile 1
http://www.bestsynoil.com/amsoil_vs_mobil1.htm

[Limbo]

DSP email sent!

[Limbo]

Larger capacity engine have greater heat emmissions, your average v8 runs at least a 25w-50 and some even 25w-75 on the higher end stuff.
Don't forget how much fuel is being burnt and how large the piston chambers are. With your Falcons with alloy heads they run 10w30 as they do not rev as high. I believe some have oil coolers also like the XR6.

My friend V8 virtually drinks mobile 1 5w50. Runs out almost as fast as it runs out of fuel! (Only 200km per 50ltr tank of 98 octane) but then its a 5.7ltr beast with over 600hp at the wheels. Which means you can't drive in a straight line. :p


also about heat generation Limbo is also right... BUT i doubt very much your average S/XR6/VRX/Camry V6 would create more heat than a high revving, high CR Type-R motor...