Oil Change, Royal Purple

[blinkwatt]

Originally Posted by pecivil

Anyway, on my boxster, there is a sticker on the trunk lid near the oil filler neck that clearly states "Use Mobil 1 0-40 ONLY"

The local dealership, "Niello Porsche" will only use Mobile 1 0-40,they will not touch anything else.

[MNBoxster]

Hi,

Most Motor Oil is multi-viscosity and uses the 4 or 5-character description such as 10W40. The 1st number is the actual weight of the Base Stock of the Oil and is followed by a 'W' - the SAE's designation for Winter operating (cold start) conditions, the last 2 numbers are the viscosity of the Oil once it reaches a theoretical operating temperature - 150° F. These types of oils are classified as 'non-Newtonian' because of this ability. A common misconception is that these Oils are actually a blend of two different weight Oils, but this is not true at all.

Modern Oils contain an additive package which includes 'Viscosity Index Improvers'. These 'V.I. Improvers' help the Oil to do the opposite of what it wants to do when it warms up - which is to thin out. V.I.I.s contain long-chain polymers which are temperature sensitive. These polymers are molecules which 'curl-up' at lower temperatures allowing the Oil to flow at it's stated weight (the 1st number). At 150° F, these polymers 'uncurl' due to the temperature and essentially make the Oil thicker so that it now has the Viscosity (the resistance to flow), or Flow rate, which is equal to an Oil with the weight of the second number.

Because of this, you want an Oil which has the lowest weight such as a 0WX oil because this oil will circulate through a cold engine faster. Then, you want the Oil to behave like a thicker Oil once the engine warms up so you want a higher 2nd number such as XW40 or 50.

But, this system is not perfect. As counter-intuitive as it may sound, you do not want an Oil which is too thick. You should never use a 50 weight Oil in a Boxster. An XW50 Oil is 20% thicker (at operating temperature) than an XW40 Oil. This means that the engine has to work 20% harder just to move the oil around inside your engine. An engine with thicker Oil produces significantly less power, uses more fuel, produces more emissions and runs hotter, all contributing to shorter engine life. A thinner oil can more easily and quickly be 'pumped-up' to the critical parts of the engine, takes less energy to move it around, helps the engine to produce more power, less emissions, better MPG. And the engine will last longer.

Porsche has determined that 0W40 is the optimal Oil to use in the Boxster, anything more is actually not better at all and with it, you won't achieve the stated MPG or Power and consequently 0-60 times or Top Speed. Using a thicker 50weight Oil will cause greater wear sooner than sticking with the recommended 0W40.

Also, Porsche specifically recommends Mobil1, not merely a synthetic. This is not due to broad availability or some SweetHeart deal they have with Mobil Oil. Mobil1 is truly the best of all the synthetics. It is produced using the PAO method (meaning it is a true synthetic with no trace amounts of Sulphur or Phosphorus which Dino Oils contain, and which are very destructive to an engine). And, Mobil1 contains only 10%-12% addditives by volume (depending upon the type). Royal Purple and RedLine contain nearly twice as many additives by volume meaning that they actually contain less Base Stock Oil/volume, in other words, there's more Oil in Mobil1 than RedLine or Royal Purple. They're not necessarily awful, but they're not as good as Mobil1.

Hope this helps...

Happy Motoring!... Jim'99

[blue2000s]

Originally Posted by MNBoxster

The 1st number is the actual weight of the Base Stock of the Oil and is followed by a 'W' - the SAE's esignation for Winter operating (cold start) conditions, the last 2 numbers are the viscosity of the Oil once it reaches a theoretical operating temperature - 150° F. These types of oils are classified as 'non-Newtonian' because of this ability.
Hope this helps...

Happy Motoring!... Jim'99

That's still technically a Newtonian fluid.

[insite]

Originally Posted by blue2000s

That's still technically a Newtonian fluid.

does viscosity vs. temperature effect the classification as newtonian or non? isn't it shear / strain vs. viscosity? my fluid mech / tribology is rusty...

[blue2000s]

Originally Posted by insite

does viscosity vs. temperature effect the classification as newtonian or non? isn't it shear / strain vs. viscosity? my fluid mech / tribology is rusty...

The specification of a Newtonian fluid is the linear relationship between shear and strain for any given temperature and pressure so the variation of viscosity with temperature (or pressure) is allowed for a Newtonian fluid.

[MNBoxster]

Originally Posted by blue2000s

That's still technically a Newtonian fluid.

Hi,

Sorry, but I don't agree.

The shear stress of a petroleum oil or other Newtonian fluid at a given temperature varies directly with shear rate (velocity). The ratio between shear stress and shear rate is constant; this ratio is termed viscosity. The higher the viscosity of a Newtonian fluid, the greater the shear stress as a function of rate of shear.

In a non-Newtonian fluid -- such as a grease or a polymer-containing oil (e.g., multi-grade oil) -- shear stress is not proportional to the rate of shear. A non-Newtonian fluid may be said to have an apparent viscosity, a viscosity that holds only for the shear rate (and temperature) at which the viscosity is determined. The shear failure point in most oils is between 4,000 and 8,000 psi. Source - http://www.lemd.com/motorsport/previous.cfm?id=19

Newtonian fluid - a fluid with a constant viscosity at a given temperature regardless of the rate of shear. Single-grade oils are Newtonian fluids. Multigrade oils are NON-Newtonian fluids because viscosity varies with shear rate. Source - http://www.oilanalysis.com/dictionary/default.asp?definitionsearch=xqxqxqxq222&alphasearch=N

Newtonian Flow - Occurs in a liquid system where the rate of shear is directly proportional to the shearing force, as with straight grade oils which do not contain a polymeric viscosity modifier. When rate of shear is not directly proportional to the shearing force, flow is non-Newtonian, as it is with oils containing viscosity modifiers. Source - http://www.chevron.com/products/prodserv/ehl/techterms.htm

I rest my case...

Happy Motoring!... Jim'99

[blue2000s]

Originally Posted by MNBoxster

Hi,

Sorry, but I don't agree.

The shear stress of a petroleum oil or other Newtonian fluid at a given temperature varies directly with shear rate (velocity). The ratio between shear stress and shear rate is constant; this ratio is termed viscosity. The higher the viscosity of a Newtonian fluid, the greater the shear stress as a function of rate of shear.

In a non-Newtonian fluid -- such as a grease or a polymer-containing oil (e.g., multi-grade oil) -- shear stress is not proportional to the rate of shear. A non-Newtonian fluid may be said to have an apparent viscosity, a viscosity that holds only for the shear rate (and temperature) at which the viscosity is determined. The shear failure point in most oils is between 4,000 and 8,000 psi. Source - http://www.lemd.com/motorsport/previous.cfm?id=19

Newtonian fluid - a fluid with a constant viscosity at a given temperature regardless of the rate of shear. Single-grade oils are Newtonian fluids. Multigrade oils are NON-Newtonian fluids because viscosity varies with shear rate. Source - http://www.oilanalysis.com/dictionary/default.asp?definitionsearch=xqxqxqxq222&alphasearch=N

Newtonian Flow - Occurs in a liquid system where the rate of shear is directly proportional to the shearing force, as with straight grade oils which do not contain a polymeric viscosity modifier. When rate of shear is not directly proportional to the shearing force, flow is non-Newtonian, as it is with oils containing viscosity modifiers. Source - http://www.chevron.com/products/prodserv/ehl/techterms.htm

I rest my case...

Happy Motoring!... Jim'99

I'm not trying to argue that a multi-viscosity non-synthetic motor oil is or isn't Newtonian, honestly, I don't know.

Your comment above suggested that the fact that the oil changes viscosity with temperature makes it non-Newtonian. This isn't what would make the oil non-Newtonian, it would be the fact that the fluid shear forces are not linear with the strain on the material.

[MNBoxster]

Originally Posted by blue2000s

I'm not trying to argue that a multi-viscosity non-synthetic motor oil is or isn't Newtonian, honestly, I don't know.

Your comment above suggested that the fact that the oil changes viscosity with temperature makes it non-Newtonian. This isn't what would make the oil non-Newtonian, it would be the fact that the fluid shear forces are not linear with the strain on the material.

Hi,

Fair enough - PEACE!...

Happy Motoring!... Jim'99