Gauge fluids

[duckbill]

I need to hear some real world experiences. I'm ready to replace the fluid in a depth gauge, and need some feedback on what works best, what works well, and what to avoid. What is known to attack painted markings, and what is safe. What is too thin, and what is too thick.

This is for a depth gauge having the leveling bubble and compass combo.
I've heard of mineral oil and silicone brake fluid being suggested. How are those? How do they compare to eachother? Any other suggestions on readily available fluids?

Thanks.

 

[Texfrazer]

I've used clear mineral oil and baby oil (mineral oil with an added scent) with success. Thus far, I haven't had any issues with it attacking the painted surfaces. The hardest part has been sealing the gauges. Often times, the sealant was sucked into the gauge just a little bit, but enough to impede the needle or compass. However, this was my fault for not being careful enough.

 

[captain]

Most liquid filled gauges use glycerin.

 

[duckbill]

Thanks, Gents.

As it turned out...
I didn't disassemble the gauge until I had everything ready to finish the job. I had purchased silicone-based brake fluid (DOT5) at $17 for, I think, a half pint or pint?:shocked2: I opted to go with the silicone fluid as the others seemed too thick and I couldn't locate any "thin" mineral oil locally.

Anyway, I unscrewed the bezel, ready for the oil to come out along with maybe the compass needle, when lo and behold the fluid was only in an encapsulated lense which also housed the compass. The space underneath where the depth gauge mechanism lay was just air.

I thought about drilling a small hole and refilling the lense, but 1) I wasn't sure how effectively I could reseal the hole, especially once it had been exposed to silicone, and 2) with my luck it is the plastic inside that is dark and hazy instead of the actual fluid.

So, thanks for the replies, and I'll store them away for next time. Luckily the seal on the brake fluid was still intact and the automotive store gave me a full refund on that bit of semi-precious fluid. The gauge, in the mean time, has been relegated to collector-only status.