When reading SAE oil grades for multi-weight oils the lower or "w" number
refers to the oil at 40C and upper number is at 100C. A common viscosity
measurement is centistokes, (cSt). SAE 50 will have a viscosity near 18 cSt
at 100C regardless of whether it is a synthetic or not. The Mobil 1 15w-50
will have a viscosity of 125 cSt at 40C. A 20w-50 will be closer to 170 cSt
at 40C. The synthetics usually have a wider viscosity index without as much
need for modifiers and their performance can shine at temperatures far away
from these standards. 

One thing that needs to be understood is that for loose tolerance engines or
those that are worn too much clearance on one side always means less or
insufficient clearance on the other side. As such loose engines can actually
be more demanding of the oil to keep the parts separated. 

As important as an oil pressure gauge is it is even more helpful the have an
oil temperature gauge. The Water boxer has a wonderful (?) ability to have
oil temperatures not follow the coolant temperature, especially at high
speeds and loads and the situation gets worse when the crankcase is over
filled. It is these high oil temps that cause the loss of oil pressure both
from viscosity loss and the case expansion letting the bearings get loose
and the pump to lose its ability to pump. The oil can go into thermal run
away and this is where we get those thrown rods. If not for this phenomenon
the Water boxer would have no problem running with a *w-30 or *w-40 oil. For
daily winter driving (to-from work) I use the 0w-40 which works just fine on
my red van which is completely stock. For summer and/or long trips I want
the 15w-50. 

Keep in mind that higher viscosity oils have their draw backs. They provide
poorer lubrication when cold and they rob power and economy. 

Dennis
 

-----Original Message-----
From: Vanagon Mailing List [mailto:vanagon@gerry.vanagon.com] On Behalf Of
Stuart MacMillan
Sent: Wednesday, May 29, 2013 12:26 PM
To: vanagon@GERRY.VANAGON.COM
Subject: Re: oils and gasoline

Ahh, these threads are so much fun!   Everyone has an opinion and an
opportunity to join in.  I can't resist.

Regarding better mileage with premium gas, if it doesn't contain 10% (it
does here in WA, you are fortunate in Canada) you will get about 3% better
fuel economy due to the lower energy content of ethanol (ethanol adds oxygen
for more complete combustion).  Since you are getting more than that, then
you probably have some carbon build up that is increasing compression to the
point where you get some knock with heavy loads on regular.

Regarding synthetic oils and viscosity, the SAE rating is "effective
viscosity," not physical viscosity.  A 15w-50 synthetic oil is physically
thinner than a 15w-50 dino oil, but the chemistry of a synthetic (more long
chain molecules of  consistent length plus viscosity extenders) offers the
same effective viscosity lubrication with higher breakdown temps in a
thinner (purer) oil. 

With its being thinner we can run into low oil pressure issues with some
synthetics in our loose WBX engines (the hotter they get the looser).
15w-50 should be fine, but 20w-50 may be needed in worn engines since it is
physically thicker than the 15w-50.   Run the 5w oils ("mileage boosting"
oil for modern cars) and you can have pressure problems at high temps. 

Which brings me to my last point.  All WBX engines should have an oil
pressure guage!  Van Caf� has a great kit at a great price (I did my
research):
http://www.van-cafe.com/home/van/page_362_263/oil_pressure_gauge_kit.html
Best money and two hours you'll spend.

I had one on my '84 and am installing this one on my '85 this weekend (and
I'll transfer it to the Subaru engine).  It didn't keep me from blowing up
my engine, but at least I knew I was on borrowed time:
http://volksweb.relitech.com/21rodbrg.htm 

For more fun reading on oil look up "tribology," which is the science of
lubrication.  You will learn that two of the best known lubricants are whale
oil and castor oil (Castrol's original formula).  

Stuart

-----Original Message-----
From: Vanagon Mailing List [mailto:vanagon@gerry.vanagon.com] On Behalf Of
James Eaton
Sent: Wednesday, May 29, 2013 5:16 AM
To: vanagon@GERRY.VANAGON.COM
Subject: Re: oils and gasoline

> 
> Date:    Mon, 27 May 2013 12:57:38 -0500
> From:    Jim Felder <jim.felder@GMAIL.COM>
> Subject: Re: Engine Oil Question
> 
> I don't think it's better, I think it's very good and moderately 
> priced. I know from many thousands of miles of experience that without 
> the right oil (of which Castol 20W50 is one) and the right filter, you 
> stand a good chance of hearing your waterboxer's oil buzzer go off on 
> a hot day of freeway driving.
> 
> It has been explained to me by people who are in the business of 
> selling oil and in the business of building engines that the 
> waterboxer does not have tolerances that would take advantage of the
synthetics' advantages.
> It's like putting high test in the gas tank;  it won't hurt the car 
> but it won't help it either, and costs more.
> 
> Jim
> 
Hmmm,

Even back in the '80s, when I had my Rabbit, we were advised that if you
wanted your engine to last you should run synthetic oil, especially if you
ran a lot under adverse or high load conditions.  And that was back when
synthetics were all thin, thin, like 0W20.  Now that synthetics are the same
weight as regular oils, only with wider range (e.g. 15W50 is the same
thickness as 20W50, except in the cold, where it's thinner for better lube
at start-up), all engines, even those needing heavier oil to cope with high
temperatures, can find a synthetic to do the job.

And I have a contrary observation to your line about premium octane
gasoline;  our '91, with 290k km, gets 2-3 mpg more on 91 octane than on 87
octane on the highway.  (The owner's manual recommends the use of 91 octane
under hot, high load conditions, which described our camping trips in
eastern Ontario last summer.)  A colleague who teaches and researches gas
engine maintenance and repair suggested that the improvement is likely due
to the superior flame front propagation properties of 91 octane under higher
loads, and to the lower alcohol content (apparently in Ontario premium does
not have to have the 5-10% alcohol that regular does).

James
Ottawa, ON
'91 Westfalia Weekender
                                          =