Re: Oil Grade ?

[jadney@vwtype3.org (Melissa & Jim)]

>From: "Gregory M. Merritt" <gregm@engin.umich.edu>

>	Note that current Bentley manuals do include multi-grades in
>their table of acceptable oils.
>
>	That said, I like to run single grade when I can... but here in
>Michigan in January, it's possible for the temperature to range from
>-20F to +60F (though -5F to +40F is more typical).  I use 10W30 here
>in the winter, and change it often (~500miles, which is about once per
>month for me.  The possible week-to-week temperature variation is just
>too great here in the winter to run a single weight oil, IMHO.

I agree.  While it is true that VW specified mono-weight oil for all their 
cars at the time they were built, the specifications for oils have changed 
very significantly in the last 25-30 years.  Around 1970 the SC-SD grade was 
the latest thing; now we are up to something like SH.  The main motivation 
for this has been the newer water cooled cars which run much hotter than 
their predecessors; they have now nearly caught up with our aircooled VWs.

The problem used to be that the additives that made an oil multi-weight did 
not stand up well to the higher temps of the air cooled cars or to 
motorcycles, which were virtually all air-cooled at that time.  Increasing 
crankcase temps of water cooled cars have forced the development of 
viscosity enhancers that last longer at high temps, and we can reap the 
benefit of this by using these.

That said, it is important to understand that our engines are still hotter 
than most water cooleds, so these additives will not last forever.  A 10W-40 
will eventually break down to a straight 10W.

Another misunderstanding is the assumption that a heavier oil is a better 
lubricant.  There are times when the heavier oil is actually worse for you 
just because it can't be pumped to the bearings as fast, and then there is 
the extra viscosity energy loss because of the thicker oil.  This is why I 
do not think the 20W-50 is a good idea for most people.

If I could find it for cheap I would buy 15W-30 for the winter and 20W-40 
for our summers; what I settle for is 10W-30 and 10W-40.

Jim
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       Melissa Kepner                                    Jim Adney
       jadney@vwtype3.org               jradney@njackn.com
                             Laura Kepner-Adney
                             Madison, Wisconsin
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