Date: Thu, 13 Sep 2007 16:29:35 -0400
Reply-To: Mike S <mikes@FLATSURFACE.COM>
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: Mike S <mikes@FLATSURFACE.COM>
Subject: Re: DOn't use SM rated oils Re: Flickering Oil Light 84 auto
In-Reply-To: <247267.9888.qm@web82706.mail.mud.yahoo.com>
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At 02:50 PM 9/13/2007, David Kao wrote...
>is which weight is best for Vanagon. Most new cars these days
>recommend 5W-30.
>These cars are more powerful and spins at higher RPM. Yet they require
>lower
>weight oil. I doubt Vanagon engines are hotter.
We're not talking about _any_ manufacturer, we're talking about VW,
which has traditionally had tribologists who are _very_ picky about
oil. And we're not talking about "most cars these days," but old
Vanagon engines based on WW2 technology.
Manufacturers are under tremendous pressure to keep MPG ratings high.
As far as reliability, in general they're only concerned with the
warranty period, or possibly the average time to trade-in (which may
actually be less).
A modern VAG engine (ATC, 1.8T) is spec'd for 0.0004-0.0016" (that's 4
TEN-THOUSANDTHS at the tight end!) radial clearance on the crankshaft,
for which they specify 5W-40 oil. The spec for the WBX engine is
.001-.004", or 2.5 times greater.
The Toyota 3MZ-FE (Sienna minivan) engine is spec'd at 0.0006-0.0012",
and they specify 5W-30.
I think this is from an aircooled, but note that VW says 20W-50 is good
for an extra 35F+ over a 10W-40.
http://www.ratwell.com/technical/OilSelection/VWOilGuidelines-SG.jpg
This is definitely from a watercooled (but not a Vanagon), again, VW
says you get an extra 40F+ at high temps, 20W-50 vs. 10W-40. This is
from 1995, so it's with pretty modern (SH) oils. Note that a 20W-50 is
good to well below freezing, and 5/10W-50/60 covers the widest range of
temperatures. In this chart, the "A" column is for "Energy Conserving"
oil, and "B" is for "Multi-Grade" oil, which I read to imply that VW
used the former in MPG testing to get better results, but you should
use the latter if engine life is more important to you.
http://www.ratwell.com/technical/OilSelection/VWOilGuidelines-SH.jpg
I'll turn your argument against you - if thinner is better, why aren't
you running kerosene in your crankcase?
Go ahead and run Mobil 1 5W-50 if you want, it will give you better
cold start performance. But know, that from long time experience, both
the manufacturer and knowledgeable users would choose a 20W-50 over a
10W-40 (which is the difference you mentioned in your original post) in
above freezing temperatures.
