You can series and parallel any number of capacitors to get the right
value. A given oscillator type works best within some range of reactance
values for L and C. If you go too far outside the ideal range, stability
will suffer, noise might increase, and if too extreme, it might not
oscillate. The ideal range depends on the oscillator design. That being
said, you can often vary L and C quite a great deal and still get
adequate operation.

Real inductors are, in general, a lot more different from their
theoretical ideal counterparts than capacitors are. Real inductors have
considerable loss and stray capacitance, as well as being temperature
sensitive. So you'll often find that a circuit works quite a bit
differently if you substitute an inductor for one with different
physical construction. For a VFO tank, I use only toroids wound on type
6 powdered iron material. (As I mentioned earlier, type 7 is probably as
good, but I've never used it.) For VFO tank capacitors, I use only NPO
ceramic. The combination produces low drift, dominated by the inductor.
If desired, the drift can be compensated by replacing part of the C with
negative temperature coefficient parts. Most other types of L and C have
substantially greater temperature sensitivity. You might get lucky and
have poor parts drift in opposite directions and more-or-less cancel,
but that's poor practice and hard to duplicate. Better to design for
minimal inherent drift, then compensate what's left if necessary.
Toroids have the big advantage of producing a relatively small external
field. That makes them much less sensitive to mounting, the influence of
nearby objects, and microphonics.

Jock Cooper wrote:
. . .
I wasn't sure if this was even OK to do (if it is too lossy or
someting), I figured I could experiment around with the result and
find out But maybe now I can just ask.. how much mucking around
can I do by adding in parallel and serial caps to tweak the variable
cap range? Also, Can I just find any old values of L and C that when
plugged in would give me the F I'm looking for? Or are there only
certain values of L and C that are appropriate for certain ranges of
Freq.

. . .

Roy Lewallen, W7EL