Looking through the VW Vanagon Maintenance booklet I was surprised to see
that VW recommends changing oil at every 7500 miles and changing the oil
filter at every 15000 miles.  All mechanics that service cars say that oil
should be changed every 3500 miles together with the oil filter.  Is this
simply providing more work for the mechanics or can the oil really work OK
up to 7500 miles?
Also if using syntetic oil, should that make it OK to increase the mileage
between oil changes?

Thanks for your input.

Sorin Bejenaru