I have used Bob's Speedometer in Michigan for my '50 Chevy COE and '47 Diamond T which both required recharge of the fluid, and replacement of the capillary tube. I was told the fluid is not just ether, but also a small amount of glycerin and alcohol. I recall that the last time it cost $180 or so. On both, I instructed them to leave the gauge face alone, for the same reasons 801curt stated. Both work great, within 2-4 degrees, which is a close as you can tell. They are listed in Hemmings or perhaps you can Google them,
Kent
