The only way to really know is to perform oil testing. This will also tell
you "why" it needs to be changed. Anything else is just a guess.
As for the factory recommendation keep in mind that in its normal
application the engine is turning less revolutions per mile and under much
less load, both weight and wind resistance. Also, if the oil capacity is
reduced (shortened pan) that will effect oil life.

For engines that are used in varying applications, oil change intervals are
based on time, (months/years), miles, operating hours, and amount of fuel
consumed. Yes, how much fuel burned? Back in September I rented a Focus down
in Florida. Even around town I beat 30 mpg and on the highway close to 40.
Over 917 miles the onboard trip computer said I did 34.7 mpg. Since the
vanagon will use almost double that the oil change intervals may need to be
cut in half. Again, the only way to know is to do some testing.

Dennis

-----Original Message-----
From: Vanagon Mailing List [mailto:vanagon@gerry.vanagon.com] On Behalf Of
Jarrett Anthony Kupcinski
Sent: Thursday, December 06, 2012 2:00 PM
To: vanagon@GERRY.VANAGON.COM
Subject: Re: Oil Change. Zetec

Every 5000 miles/6 months assuming normal operating conditions. 3000 miles
for extreme service conditions. The Bostig recommendation matches Ford's.

-Jarrett K
89 Westy powered by Bostig
> What did the engine manufacturer recommend for the engine when it was new
in a factory installation?
>
>> Bostig recommends an oil change every 3 to 5K using synthetic oil. Since