Compass Oil

[DaveOnCudjoe]

The oil inside my steering compass, a Suunto, has leaked or evaporated away and I want to replace it. No help from the manufacturer so I'll ask here, what is a suitable liquid to replace the original fluid? Thanks all, David

[Ziggy]

You didn't say what brand of compass you have. From the FAQ on the Ritchie navigation web site:

What type of fluid is in my Ritchie Magnetic Compass?
Until 2001, all Ritchie compasses (see exception) were filled with odorless mineral spirits. Ritchie now uses a fluid called Isopar L® that has similar properties but some added benefits over odorless mineral spirits. These can be mixed together.

Exception: Some old style Flat Top Compasses used a mix of isopropyl alcohol and water. This process was stopped in the 1960s. If you have a Flat Top Compass, it is recommended that you test the fluid to see if it is odorless mineral spirits or isopropyl alcohol.

[Wotname]

As Ziggy quoted, most use a mineral oil but some older (very) used isopropyl alcohol (usually mixed with water). You can tell by the smell or feel of each.

While you can buy compass fluid (try aircraft instrument suppliers) you can get by using a clear kerosine at a pinch.

[SabreKai]

I refilled the compass on my old Grampian with mineral oil from a pharmacy. I believe it was a Ritchie but not sure. Anyway it was partly full of oil of some sort, the mineral oil didn't react adversely and it served for as long as I owned the boat.

[vintageray]

I bought a quart of compass fluid for my Ritchie compass. It's called Isopar L and is compatable with the older fluid. Got it at West Marine. I think it was like $17.00.

[S/V Illusion]

I assume you have already determined why it leaked and replaced the part(s). Otherwise, replacing the fluid in an exercise in futility.

[sdowney717]

mineral oil is too thick to let the compass wheel move especially when cooler.
odorless mineral spirits is just right.
I replaced a Richie diaphram and was not too hard.
I also to get the dissolved air out of the fluid, you fill it and seal it and put it in the freezer. The fluid contracts and the air comes out
of the fluid. Then you have to purge the air bubble from the compass.
The goal is to not have an air bubble in the glass at the top.