Oil change intervals

[ggrunwald@domain.elided]

Hi all.  Possibly like many of you my Stag is not my daily driver,
consequently it does not do many kilometres.  I have always worked on
changing the oil each 6mths or 5000kilometres, which ever comes first.  I
have also always changed the filter each 5000 kilometres.  Generally this
arrangement results in an oil change at six months and the filter change
every second oil change.  I do not use synthetic oil but a good quality
mineral oil with a 25-70 rating.

I have been told recently that I can stretch the oil change to 12 months or
5000kilometres, that is miss the intermediate oil only change.  I have some
concerns about this.  Does oil degrade significantly if the car is not
getting much use?  Note that when I do use the car it always runs for 30 to
40 kilometres, never short hops.  Any comments?

Guy Grunwald.