A quick Google search yielded this link to a seller of compass oil:

http://www.discountweather.com/compassoil.html

Recently, I had a diving compass with a bubble large enough to disrupt
its function.

I successfully removed and replaced the bubble with compass oil by
immersing the compass in enough compass oil to cover the fill port
while held upright in a clear plastic sandwich bag. Gentle squeezing
and relaxing of the body of the compass forced the air out and drew oil
in.

Your situation is easy as you can close things up with the port screw
cap. I had to clean and epoxy the hole I had drilled at the leak point.
8^)

Previously, I had tried using a fine gauge syringe (28g), but the
surface tension of the oil interfered with the process, always leaving
a little bubble.

Actually, a little bubble won't interfere with the function, but the
first method was easier and completely successful.

I had considered using mineral oil, but it was a little thicker than
the compass oil.

Then, in a rare flash of my packrat memory, I found an old
non-functioning boat compass that I kept just for future tinkering.
That was my source of compass oil. Hey, one out of 10,000 makes it
worthwhile to packrat, IMO!  8^)

There may be adequate substitutes to compass oil, though.

Good luck.

Dave C

A quick Google search yielded this link to a seller of compass oil:

http://www.discountweather.com/compassoil.html

Recently, I had a diving compass with a bubble large enough to disrupt
its function.

I successfully removed and replaced the bubble with compass oil by
immersing the compass in enough compass oil to cover the fill port
while held upright in a clear plastic sandwich bag. Gentle squeezing
and relaxing of the body of the compass forced the air out and drew oil
in.

Your situation is easy as you can close things up with the port screw
cap. I had to clean and epoxy the hole I had drilled at the leak point.
8^)

Previously, I had tried using a fine gauge syringe (28g), but the
surface tension of the oil interfered with the process, always leaving
a little bubble.

Actually, a little bubble won't interfere with the function, but the
first method was easier and completely successful.

I had considered using mineral oil, but it was a little thicker than
the compass oil.

Then, in a rare flash of my packrat memory, I found an old
non-functioning boat compass that I kept just for future tinkering.
That was my source of compass oil. Hey, one out of 10,000 makes it
worthwhile to packrat, IMO!  8^)

There may be adequate substitutes to compass oil, though.

Good luck.

Dave C

I'm not sure if the SPG is filled with compass oil, but a quick Google
search yielded this link to a seller of compass oil:

http://www.discountweather.com/compassoil.html

There may be someone here who knows if other oils or glycerin would be
more suitable.

Recently, I had a similar issue, but with a diving compass which had an
air bubble large enough to disrupt its function.

I successfully removed and replaced the bubble with compass oil by
immersing the compass completely to cover the fill port while held
upright in a clear plastic sandwich bag.

Gentle squeezing and relaxing of the body of the compass forced the air
out and drew oil in.

Your situation is easy as you can close things up with the port screw
cap. I had to clean and epoxy the hole I had drilled at the leak point.
8^)

Previously, I had tried using a fine gauge syringe (28g), but the
surface tension of the oil interfered with the process, always leaving
a little bubble.

That not a problem in a compass but I think it will affect accuracy of
an SPG.

I had considered using mineral oil in my compass repair, but it was
definitely thicker than the compass oil.

Then, in a rare flash of my packrat memory, I found an old
non-functioning boat compass that I had kept just for future tinkering.
That was my source of compass oil.

Hey, 1 out of 1000 makes it worthwhile to packrat, doesn't it?  8^)

Good luck.

Dave C