Date:         Sat, 24 Apr 2004 10:28:12 -0500
Reply-To:     Joel Walker <jwalker17@EARTHLINK.NET>
Sender:       Vanagon Mailing List <vanagon@gerry.vanagon.com>
From:         Joel Walker <jwalker17@EARTHLINK.NET>
Subject:      Re: Distance windows for various maintenance checks?
Content-Type: text/plain; charset="iso-8859-1"

> Any opinion on the large discrepancy in distances?  Is the Mechanic
shop
> sand bagging or compensating for people that can't identify
burgeoning
> problems?  Waddya think?

vw always said 5000 km. makes for nice round numbers.
but that's about 3000 miles. and what i found was that the oil
analysis i used to have done showed a straight 30w oil would turn into
a 46w oil by 3000 miles. so i started looking around and found some
stuff done by oil companies that showed the viscosity of motor oil
began to change at about 1800 to 2000 miles. that is, that's the
mileage when a 30w first starting not being a 30w anymore.
so i dropped my oil change intervals down to 2500 miles ... that also
made for nice round numbers. :) easier to divide into than 3000.
sometimes, if it's been particularly hot or cold, i'll even change at
2000 miles.

but it's a personal thing ... between you and the oil and the bus.
if you drive a lot of short trips, change the oil more often.
if you drive a lot on dusty roads or countryside, change the oil more
often.
if most of your driving is highway trips of several hundred miles, you
don't need to change the oil as often (but you DO need to check it
often!!).

nowadays, oils are a lot better and able to stand up to longer
distances. but one of the things that oil analysis showed was that a
change is necessary not just for the viscosity change ... there are
acids that are formed by combustion that work their way into the oil
(the piston rings are never completely able to keep gases out of the
engine oil), and crud that makes its way into the crankcase. the
filter helps keep a lot of this out of the oil, but never all of it.
so you need to change the oil to help get rid of this stuff as well.
there was one fellow, long ago, who used to just add baking soda to
his oil every 1000 miles ... to neutralize the acids. claimed it
worked just fine.

one of the other important reasons for changing oil is to SEE what's
going on with the engine. this opportunity was lost to us when
hydraulic valve lifters were introduced ... now you no longer needed
to crawl under the engine ever other month, so small problems went
unnoticed. :(

but the best rule of thumb i've ever heard was this ...

change the engine oil every three months or 3000 miles, whichever
comes first, in summer;
change the engine oil every TWO months or 2000 miles, whichever comes
first, in winter.

good luck!
joel