why use 10w-60 in a gtr??

[meet07]

I know if because of sponsorship but I was wacthing a video of a high horsepowered gtr and he mentioned that he is using castrol 10w-60. Why such a thick oil?? Is there some little secret that im missing?

[Sil240]

be careful someone may have broken an oil pump by running some really thick oil.
Watch you oil pressure

[meet07]

ohh im not trying it. Just wondering why?

[gawdzilla]

a lot of race motors are built "loose" aka with much higher than OEM spec oil clearances. this can yield more power due to less friction. you then need to run a thicker oil make up for the looseness of the motor. in general, a motor with OEM clearances should be run with OEM spec oil. some people think putting a thick oil in their motor and straining the pump is good for the motor because the oil pressure is reading higher. i wouldn't consider these people smarter than the engineers that designed the motor and wrote the FSM.

[mcfly]

Just to clear this up, 10w60 is not a thick oil.

[Joe]

uh 60 weight is pretty damn thick for a street car.

[mcfly]

yes 60W is thick

10w is not.

[meet07]

a lot of race motors are built "loose" aka with much higher than OEM spec oil clearances. this can yield more power due to less friction. you then need to run a thicker oil make up for the looseness of the motor. in general, a motor with OEM clearances should be run with OEM spec oil. some people think putting a thick oil in their motor and straining the pump is good for the motor because the oil pressure is reading higher. i wouldn't consider these people smarter than the engineers that designed the motor and wrote the FSM.

Why loose?? I would think that loose would cause things to fall apart....

[Cjmartz2k]

yes 60W is thick

10w is not.

You don't understand how multi-weight oils work. Joe does.

[Cjmartz2k]

Viscosity is the most misunderstood aspect of oil and yet it is the most important.

Viscosity is the force required to shear (break) the oil at a certain speed and temperature. Oils work because they have viscosity; the drag of a rotating part pulls oil from a low-pressure area into a high pressure area and “floats” the surfaces apart. This is called “hydrodynamic lubrication” and crank bearings depend on it.

Oil must be capable of flowing at low temperatures, so that it gets around the engine in a fraction of a second at start-up and must protect engine components at high temperatures without evaporating or carbonising and maintain adequate oil pressure.

The numbers on every can of oil indicate its performance characteristics when new but there are many misconceptions on what these numbers actually mean.

For multigrade oils you will see two numbers (for monograde oils only one). The first is followed by a “w” and is commonly 0, 5, 10, 15 or 20. The second number is always higher than the first and is commonly 20, 30, 40, 50 or 60.

The first and second numbers ARE NOT related.

The “w” number (0, 5, 10, 15 or 20)

When multigrade oils first appeared, a low temperature test called “w” (meaning “winter” not weight) was introduced.

Using a “Cold Crank Simulator, the test measures the oils ability to flow at low temperatures.

ALL oils are THICKER at low temperatures than at high temperatures but the lower the “w” number, the quicker the oil will flow at low temperatures.

The second number (20, 30, 40, 50 or 60)

This number is known as the SAE (Society of Automotive Engineers) number and is measured in “Centistokes” (cst) at 100degC.

Centistokes (cst) is the measure of a fluid's resistance to flow (viscosity). It is calculated in terms of the time required for a standard quantity of fluid at a certain temperature to flow through a standard orifice. The higher the value, the thicker the oil.

An oils cst at 100degC determines it’s SAE rating within the following parameters.

SAE 20 = 5.6 to less than 9.3cst
SAE 30 = 9.3 to less than 12.5cst
SAE 40 = 12.5 to less than 16.3cst
SAE 50 = 16.3 to less than 21.9cst
SAE 60 = 21.9 to less than 26.0cst

a decent oil always falls in the middle of the spec so an SAE 40 will be around 14cst.

ALL oils labelled 40 must fall within the SAE parameters at 100degC so everything from a monograde 40 to multigrade 0w-40, 5w-40, 10w-40, 15w-40 are the same thickness at 100degC.

Summary

Cold start.

A 5w-40 will flow better than a 10w-40.
A 10w-50 will flow better than a 15w-50
A 5w-40 is the same as a 5w-30

At operating temperatures.

A 10w-50 is thicker than a 10w-40.
A 15w-50 is thicker than a 5w-40
A 0w-40 is the same as a 10w-40

Multigrades offer flexibility but manufacturers recommended viscosities should be observed unless modifications have been made that affect engine temperatures or the car is being used off road.

[Cjmartz2k]

In real world application, at hot idle, your oil temps will be around 90-95c (195-205'ish F). That means at hot idle, 10W-60 will be ever so slightly thinner than straight 60W at the same temp. Heat both oils up to 100C (212F) and they should have the same viscosity. The 10W part of 10W-60 means the oil will flow no slower than straight 10W oil at cold start (and I can't remember the measured temp for the figure, sorry.)

[gawdzilla]

Why loose?? I would think that loose would cause things to fall apart....

less mechanical friction allows everything to spin a bit easier and reduces frictional loss.

[Cjmartz2k]

I think if you have ANY mechanical friction from bearing clearances (tight ones specifically, but any in general) you have more problems then just less hp. The bearings should never make contact. Now lighter weight oil would cause less drag on things like the oil pump and cut down on hp loss from windage. I believe that they build loose motors for sustained high rpm track cars because it will flow more oil for the same pressure. That should help with cooling everything down. That's how I interpret it.

[RustspecS13]

The other thing Ive heard, is track motors get very hot. Which is pretty obvious. That extra temperature makes the metal expand more and that isn't good for bearing clearances and piston to cyl wall clearances.

So you build it loose to make sure when everything is a million degrees, theres still plenty of room so bearings never touch and all that fun stuff.

~Alex

[Sil240]

Cjmartz2k - Droppin some knowledge on dat @ss!
mine too

Thank you sir!!

[Cjmartz2k]

Cjmartz2k - Droppin some knowledge on dat @ss!
mine too

Thank you sir!!

LOL, thanks, but I can't take the credit for that kick a** explination. I grabbed it off another board. It's the way I've always understood it, but articulated much better than I ever could

[Joe]

yes 60W is thick

10w is not.

yea...

go hide under your table.