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Re: [T3] oil pressure


On 19 Apr 99, at 13:33, oligeo wrote:

> -Is this normal for t-3s? I haven't had this problem on my t-1 or t-2
> except when the t-2 needed an overhaul.  Also is there any thing wrong
> with switching from single to multigrade.  I thougÈÇ8alled reading
> somewhere that you should stick to single grade with vws( I believe Muir
> said that.) Also take into account our summers generally stay in the upper
> 90s to 100 with high humidity.Maybe a 20w50? I dont want to blow any
> seals. 

This should be the same as beetles and buses: seldom happens when 
new, but gets worse as the engine wears. I would guess that a lot 
depends on when your particular oil pressure switch trips--there's 
bound to be some amnufacturing variation.

Originally VW recommended only straight weight oils, because the 
viscosity enhancers that were used in multigrade oils broke down with 
the heat of an air cooled engine. A lot has happened in 30 years of 
oil development, however, and modern oils have to meet tougher 
standards to work in modern water cooled engines, which run hotter 
than they used to. In my opinion, it is safe to use them in our cars 
now.

I am not a fan of extra heavy oil. They will certainly make the gauge 
read higher, but the thing that is important is that the oil get into 
the bearing where pressure is developed hydrodynamically in just the 
places it is needed. The pressure you read on your gauge only 
indicates what the pressure is at the gauge. Heavier oil means that 
it takes longer for oil to get to the bearing after startup. My 
feeling is that heavy grades of oil may make US feel better, but they 
don't really help the bearing.

Of course if your car lives in 130 F all the time, then things might 
be different, but it's important to keep in mind that the internal 
operating temp of your engine is about 165 F, so it really doesn't 
notice a mere 100 F too much.

Jim


-
*******************************
Jim Adney, jadney@vwtype3.org
Madison, Wisconsin, USA
*******************************

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