Re: [T3] 60 weight oil in an 1835

["Jim Adney" <jadney@vwtype3.org>]

On 13 Sep 2000, at 5:59, SIR.LANCE . wrote:

> i just put 60 weight oil in my 1835,
> seems to be ok, anything i should look for just in case im wrong?
> 
> but i can drive and after its at temp i still have 20 psi =]

What your engine needs is flow more than pressure. Of course 
there is pressure in the bearing itself, but that pressure (assuming 
there is a sufficient supply of oil) is generated by the dynamics of 
the rotating parts and has VERY little to do with the pressure we 
measure at the oil cooler exit.

By going to a heavier weight of oil you do several things: 

You increase the amount of power that the engine has to divert to 
drive the oil pump, reducing the amount of power available 
elsewhere. 

You increase the stresses on the oil pump, making it wear faster 
and increase the chances of its failing, although this is remote.

You increase the shear losses in the bearings, futher reducing the 
output power. 

You reduce the flow of oil to all parts of the engine, increasing the 
chances that some part may be starved of oil. This effect is small, 
because the oil pump is close to being a positive displacement 
pump.

If your engine is old and worn out, a heavier oil may be necessary 
to allow the hydrodynamic effects to still work in the bearings 
which have clearances much too large. In a fresh engine there is no 
reason to do this.

-
Jim Adney
jadney@vwtype3.org
Madison, WI 53711-3054

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